Write an equation and solve: Four times a number, decreased by 4 is 8.

Let's call the number "x".

The equation can be written as:
4x - 4 = 8

To solve for x, we can add 4 to both sides of the equation to isolate the 4x term:
4x - 4 + 4 = 8 + 4
4x = 12

Now, divide both sides of the equation by 4 to solve for x:
4x/4 = 12/4
x = 3

So, the solution to the equation is x = 3.