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### Course: 7th grade (Illustrative Mathematics)>Unit 4

Lesson 6: Lesson 10: Tax and tip

# Interpreting linear expressions: diamonds

We match the expressions to their meaning in this example. We're reinforcing our knowledge of linear expressions. Created by Sal Khan.

## Want to join the conversation?

• I'm confused. why is there more then one way to do a problem. so annoying.
(0 votes)
• I think it's awesome for there to be more than one way. Then you can pick out which way is best for you and then the whole problem will be easier to solve.
(29 votes)
• When Khan Academy makes a Borderlands reference
(20 votes)
• seriously, i am losing my mind right now
(15 votes)
• What is really a linear expression?
(0 votes)
• Okay, because nobody has been able to expressly define what a "linear expression" is, but rather they have been defining "linear equation" for you, I'll try to come up with one for you. I can't find any readily available definition of "linear expression" online or I'd direct you to it.

So here it goes: A linear expression is one that has a variable in it. Also, no variable is raised higher than a power of 1 or used as a denominator. So you can't divide by a variable.

So if a linear equation is commonly expressed as "y= mx+b", a linear expression would be expressed as mx+b. (by definition an expression can't have an equal sign in it or it would be an equation)
(39 votes)
• why the heck is this guys name "handsome jack"
that seems kinda self centered if you ask me.
(10 votes)
• It's a Borderlands 2 reference.
(6 votes)
• This unlearns everything I learnt in elementary
(7 votes)
• What did you learn in elementary? There is no such thing as a pony made of diamonds?
(6 votes)
• If its a pony made of diamonds, is it rlly a pony or just a diamond statue.
(9 votes)
• Diamond Statue
(1 vote)
• At , when Sal put the three other tiles into the "not used" section, one tile was 0.75p. This made me think that another way to solve the total bill could have been 2p-0.75p. That would have simplified to 1.25p. Is my way of thinking also applicable to the problem?
(6 votes)
• What does 2P - .75p mean? 2P would be the cost of two ponies, and then you would have had to add 25% tax so that would be 2P(.25) = .50P, so cost of 2 ponies would be 2.50P, divide by 2 to get 1 to be 1.25P. .75P has no meaning within the context of the problem that I can figure out.
(6 votes)
• Wow, this is harder than it seems o.0
(8 votes)
• so if the tax so impotent why did they just do nothing
(7 votes)
• 'Cause it's Khan Academy!
(3 votes)
• does anyone know how to switch ur avatar lol 😂😂😂
(7 votes)

## Video transcript

Handsome Jack is buying a pony made of diamonds. The price of the pony is P dollars. And Jack also has to pay a 25% diamond pony tax. Match the expressions to their meaning for Handsome Jack. And they say multiple expressions may fit the same description. So in this bucket, we have the price of the diamond pony before tax. Well, they already tell us that the price of the diamond pony is P dollars. So that's P right over here. Now over here, they say the amount of tax Handsome Jack pays. Well, he pays a 25% diamond pony tax. So whatever the price is, he's going to pay 25% of that. Or another way of thinking about it, he's going to pay 25% is the same thing as 0.25. So 0.25 times P is the amount of tax he's going to pay on this diamond pony. Now, they say Handsome Jack's total bill for the diamond pony. Well, he's going to pay P for the pony plus 0.25P in taxes. So that is this one right over here. P for the pony plus 0.25P for the taxes. So that's that one over there. But if we look at this, you could view this literally as 1P plus 0.25P's. Well, that's the same thing as 1.25P. So that's the same thing as this right over here. So it's 1.25P. And these other three don't seem to fit in any of these categories. So I'm going to put it into the not used. We're required to categorize everything. So let me put this in the not used. It's falling off the screen, I realize. Let me put this in the not used. And then let me put this in the not used. Let's check our answer. We got it right.