You have to move variables on one side and constants on the other aby - b + b = c + b aby = c + b y = (c + b)/ab
Start by adding b to both sides:
[tex] aby = b+c [/tex]
Divide both sides by ab:
[tex] y = \dfrac{b+c}{ab} [/tex]
This means that we must impose that [tex] ab\neq 0 [/tex] which means that neither a nor b can be zero.
