Answer: x = 5
Step-by-step explanation:
1. Set the two given expressions equal to each other (because the problem says they are interchangeable)
-5x = -40+3x
2. Subtract 3x from -5x to have x on one side of the equation.
-8x = -40
3. Divide each side by -8 to get the value of x.
x = 5
