The sum of the real numbers x and y is 11. Their difference is 5. what is the value of xy?

x + y = 11 and x - y = 5. The y's cancel so you're left with 2x = 16. So x = 8. Plug x back in to one of the original equations to find y. 8 + y = 11. So y = 3. And 3 times 8 = 24.