You have the following equation:
3(1/2 - y) = 3/5 + 15y
In order to solve the previous equation you proceed as follow:
3(1/2 - y) = 3/5 + 15y eliminate parenthesis
3/2 - 3y = 3/5 + 15y multiply by 5 both sides
15/2 - 15y = 3 + 75y multiply by 2 both sides
15 - 30y = 6 + 150y sum 30y both sides and subtract 6 both sides
15 - 30y + 30y - 6 = 6 + 150y + 30y - 6 simplify
9 = 180y divide by 180 both sides
9/180 = 180y/180 simplify
1/20 = y
(the multiplication by 5 and 2 is for eliminating denominator with the same number)
Hence, the solution to the given equation is y = 1/20
