Leon has 4 boxes. each box has 15 golf balls and 12 tennis balls.
which expression shows the total number of balls leon has in the boxes?
a. 4 × 12 × 4 × 15
b. 4 + 12 + 4 + 15
c. (4 × 15) × (4 × 12)
d. (4 × 15) + (4 × 12)

step-by-step explanation:

step 1: solve one of the equations for one of the variables. let's solve the first equation for y:

step 2: substitute that equation into the other equation, and solve for x.

step 3: substitute x = 4 x = 4 x=4 into one of the original equations, and solve for y.