The sum of the real numbers x and y is 25. Their difference is 18. What is the value of xy ?
x + y = 25
and
x - y = 18
Use elimination
2y = 7
y = 3.5
x = 21.5
xy = 21.5*3.5 = 75.25 or as a mixed number, 75 and 1/4.
