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Lesson 2: One-step addition and subtraction equations

In this math lesson, we learn to solve simple equations with one variable. We isolate the variable by removing other terms on the same side. For example, if a + 5 = 54, we subtract 5 from both sides to find a = 49. Finally, we check our solution by substituting the value back into the original equation. Created by Sal Khan.

## Want to join the conversation?

• why is there a pic of queen Elizabeth just chillin'?
• No idea maybe he just thought it'd get our attention, thus leading him to displaying it.
• Am i color blind? or is Sal? because he keeps saying in his videos "this shade of green" and i see yellow.... not green...
• There is some color variation between computer screens. On Sal's system, it may look more green than on yours.
• what do you do if the variable is in the midlle of both numbers for example -10.74=u- (-11)
u-(-11) = -10.74
You can switch the sides of an equation. Now the "u" is not in the "middle" of the numbers. Though, I would argue it was never in the middle of the numbers because the equals symbol is really separating the "u" from the number on the left side.
• How do I fix an equation like 44-q = 11 It's simply a true / false answer in my pre-algebra book. The answer is simple, it's 33. However, I do not know how to configure the equation. The example in the video shows the variable minus the number equals the difference. But what happens when the number is first and the variable is subtracted from the number? How can I configure this equation so that future equations that can not simply be solved without showing the work can be solved?
• You have 2 options...
Option 1
Subtract 44 from both sides: -q = -33
Then, you need to divide both sides by -1 to change -q into just q: q = 33

Option 2
Add q to both sides: 44 = 11 + q
Then subtract 11 from both sides: 33 = q

Hope this helps.
• Why do some numbers get canceled out?
• Some got canceled out because when if you do something like subtraction, you will get 0. If you do division, you will get a 1, and it is already assumed there is a 1 in front of a variable.
• why do we use letters in math??
• Letters are variables which we use to represent different numbers or equations like y-y1/x-x1 or y=mx+b=y=3/1+2/3
• A= 49 ez
• thx for the answer ts