Isolate the x. Note the equal sign. What you do to one side, you do to the other. First, add 1/3y to both sides
8x - 1/3y (+1/3y) = 15 (+1/3y)
8x = 15 + 1/3y
Divide 8 from both sides
(8x)/8 = (15 + 1/3y)/8
x = 15/8 + 1/24y
x = 1/24y + 1.875
x = 1/24y + 1.875 is your answer
hope this helps