Find the value of x so that the mean of {5x, 3/2x, x+9, -x} is -1.

a. 2
b. 1/2
c. -1/2
d. -2

My answer is d. Is it correct.

then (5x + (3/2)x + x+9 - x)/5 = -1

5x + (3/2)x + x+9 - x = -5
5x + (3/2)x + 9 = -5
10x + 3x + 18 = -10
13x = -28
x = -28/13

My answer verifies, check your typing.

(5(-28/13) + (3/2)(-28/13) + 9 = -5