Question

The sum of three integers is 15 . If two of them are (-11) and 7 find he third number

Answer 1

here's your ans
let third be x
-11+7+x = 15
-4+x = 15
x = 15+4
x= 19
hope it helps

Answer 2

$let \: the \: third \: integer \: be \: x \\ - 11 + 7 + x = 15 \\ - 4 + x = 15 \\ x = 15 + 4 \\ x = 19 \\ so \: the \: third \: number \: is \: 19$