The sales representative here tells you they also have two floor plans available, but they only have 24 homes available. Write an equation that illustrates the situation. Use x and y to denote floor plan #1 and floor plan #2 respectively.

Nx + Ny = 24

Nx is the number available in plan 1.
Ny is the number available in plan 2.

x and y are subscripts, not multiplying constants.