3) 15 - 2x = 3x
Add 2x to both sides so only one side contains the variable x.
15 = 5x
Divide both sides by 5.
x = 3; if you want to check your solution then plug x back into the original equation.
15 - 2(3) = 3(3)
15 - 6 = 9 ⇒ 9 = 9 so this would be true, your answer is correct.
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15) 10(2y + 2) - y = 2(8y - 8)
Distribute 10 and 2 inside their respective parentheses.
(20y + 20) - y = (16y - 16)
Combine like terms on the left side of the equation.
19y + 20 = 16y - 16
Subtract 16y from both sides.
3y + 20 = -16
Subtract 20 from both sides.
3y = -36
Divide both sides by 3.
y = -12