Add 15 to a number then then multiply the result by 3 the answer is the same as subtracting 4 from the number and multiplying the result by 5
x = number
( x + 15 ) ∙ 3 = ( x - 4 ) ∙ 5
3 x + 45 = 5 x - 20
Subtract 3x to both sides
45 = 2 x - 20
Add 20 to both sides
65 = 2 x
2 x = 65
x = 65 / 2 = 32.5