Solving for a quantity of interest is an important skill to learn. It can come in very handy when you know the value of one algebraic symbol but not another.

For example, in the formula $A=pb+y$A=pb+y, the value $A$A is by itself on the left-hand side of the equals sign. In common language, we might say that it has been "solved for" because it is by itself, even though we do not yet know its value.

When we previously tried to solve equations, we took steps to get the variable by itself. When solving for a quantity of interest, we might have more than one variable, but we still use a similar process:

Group any like terms

Simplify using the inverse of addition or subtraction.

Simplify further by using the inverse of multiplication or division.