x = -6.4
First, you would subtract 8 on both sides:
-2.5x + 8 - 8 = 24 - 8
The 8 cancels out on the left side of the equation, and 24 - 8 = 16
Next, divide both sides by -2.5, to get rid of the number that is multiplying by x.
-2.5x/-2.5 = 16/-2.5
= x = -6.4
*Remeber, when dividing a negative by a positive, the answer is negative. In this case, 6.4 is negative.