Question

If $x + y = 7$ and $x - y = 9$, find the product of x and y

Answer 1

Let $x + y = 7$ be equation no. 1
And $x - y = 9$ be equation no.2

Add both the equations-
($x + y) + ($x - y) =7$ + 9$
2$x = 16$
x = 16$/2$
x = 8$