Answer:
Is this what you meant?
(2x + 3x) × (3 + 15) = 12x + 36
(5x) × (18) = 12x + 36
90x = 12x + 36
78x = 36
x = 36 / 78
x = 18 / 39
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or
3(2x+3x) + 15 = 12x + 36
10x + 15 = 12x + 36
-21 = 2x
2x = -21
x = -21/2
