If the sum of two positive integers is 18 and the difference of their squares is 36, what is the product of the two integers?  Options
A) 108
B) 80
C) 128
D) 135
E) 143

Rationale: "let the 2 positive numbers x and y x + y = 18 - - 1 x ^ 2 - y ^ 2 = 36 = > ( x + y ) ( x - y ) = 36 - - 2 using equation 1 in 2 , we get = > x - y = 2 - - 3 solving equation 1 and 3 , we get x = 10 y = 8 product = 10 * 8 = 80 answer b"
Answer: B