The sum of two numbers is 40 and their difference is 6.5 what is their product

Let x = first number, and y = second number. 
x + y = 40 (1)
x - y = 6.5 (2)

Rearrange (2) 
y = x - 6.5 (3)

Sub (3) in (1)
x + (x - 6.5) = 40 
2x - 6.5 = 40
2x = 33.5 
x = 16.75 (4)

Sub (4) in (1) 
16.75 + y =40
y = 23.25 

x * y = 16.75 * 13.25 = 221.9375

The product is 221.9375

the answer is d.

by: nicholas dooley