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Answer:
c) x = 6
d) x = 2
Explanation:
In general, you want to "undo" what is done to the variable.
When variable terms are on both sides of the equal sign, you want to collect them on one side of the equal sign first. I like to do that by adding the opposite of the variable term with the lowest (most negative) coefficient.
Whatever you do to one side of the equation must also be done to the other side.
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c) 2(x +3) = 18
x +3 = 9 . . . . . . divide both sides by 2
x = 6 . . . . . . . . . subtract 3 from both sides
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d) 2x +15 = 27 -4x
6x +15 = 27 . . . . . . . add 4x to both sides
6x = 12 . . . . . . . . . . . subtract 15 from both sides
x = 2 . . . . . . . . . . . . . divide both sides by 2