Sample Response: Solving the equation gives only the number of upper-level seats, but that value can be used to solve for the other unknown values. To find the number of seats in the middle and upper levels, substitute the value of the variable into the expressions for the number of seats on those levels.
Use the value for the variable to solve for the other unknowns. Substitute the value for the variable into the expression for the number of seats on the middle level. Substitute the value for the variable into the expression for the number of seats on the lower level.
