First, let's solve the first equation: -20 = 40

To solve for x, we need to isolate x by adding 20 to both sides:

x = 60

Next, let's solve the second equation: x + 15 = 45

Subtract 15 from both sides:

x = 30

Now, let's solve the third equation: 96 - x = 30

Substitute the value of x we found from the second equation:

96 - 30 = 30

66 = 30

This equation is not true, so there must have been an error in our calculations. Let's go back and double-check our work:

The correct answers are x = 60 for the first equation, x = 30 for the second equation, and x = 66 for the third equation.