In order to solve for x, we must do the following:
5(x - 10) = 30 - 15x
5x - 50 = 30 - 15x (Expand 5(x - 10) )
5x - 50 + 50 = 30 - 15x + 50 (Add 50 to both sides of the equation)
5x = 80 - 15x
5x + 15x = 80 - 15x + 15x (Add 15x to both sides)
20x = 80
20x/20 = 80/20 (Divide both sides by 20)
x = 4
Therefor, the correct answer is the second option (x = 4).
You can always check if this is correct by substituting your answer back into the original equation and seeing if the left side is equal to the right side (this is also a potential method for solving the question itself if it is multiple choice, but I find it is often better to actually solve the equation rather than substitute each answer to see which works):
5(x - 10) = 30 - 15x
if x = 4:
5(4 - 10) = 30 - 15(4)
5(-6) = 30 - 60
-30 = -30
The two sides are equal, therefor x = 4 is confirmed as the correct answer.
