One number is four times another. the greater number is x. write an expression for the lesser number.

Let's call the smaller number y.

We know that four times the smaller number is equal to x. So, four times y is equal to x. Turning this into an expression, you get 4y = x. This means, to get y on its own, we need to divide by 4 on both sides, giving us the answer of:

y = x/4