Solve z = 3x + 5xy for y

z = 3x + 5xy

move 3x to the other side

sing changes from + 3x to - 3x

z-3x=3x-3x+5xy

z-3x=5xy

divide both sides by 5x to get y by itself

z/5x-3x/5x=5xy/5x

cross out 5x and 5x

divide by 5 and x

then becomes 1*1*y=y

-3x/5x (cross out x and x)

then becomes - 3/5

Answer:

y=z/5x-3/5

y=z/5x-3/5