Question

Find the value of x . 12.5,−10,−7.5,x ; The mean is 11.5 .

Answer 1

There are four values, including the unknown value x. The sum of the four values is the given value of the mean, 11.5, multiplied by four. Let S be the sum of the four values. Then we can write:
$S=11.5\times4=46$

$46=12.5 + (-10)+(-7.5)+x$
x = 46 + 5 = 51
The answer is: The value of x is 51.