Solve the equation: 4x - 7 = 21.
Sure, here's how you solve that equation:

Given the equation 4x - 7 = 21, the goal is to isolate x.

First, add 7 to both sides of the equation:

4x - 7 + 7 = 21 + 7

This simplifies to:

4x = 28

Now, divide both sides by 4:

4x / 4 = 28 / 4

This simplifies to:

x = 7

So, the solution to the equation 4x - 7 = 21 is x = 7.