Solve for x in the literal equation - 13 = xy + z.

-13 = xy + z ... subtract z from both sides

-13 - z = xy ... divide both sides by y

(-13 - z) / y = x

Okay so what you have to do is subtract Z first on both sides. that gives you

-z-13 = xy. then you divide y on both sides to get x alone. that gives you

(-z-13) / y = x and that's your answer. when there variables you can't exactly solve it down to one answer but now you have x alone.