8 less than 1/3 a number n is - 13

Let's set up an equation.

so we know the answer is - 13.

1/3 of a number (our variable) can be written as 1/3n.

8 less than that would be subtracting 1/3n by 8

so we have - 13 = 1/3n - 8.

To solve:

Add 8 to both sides: - 5 = 1/3n

Multiply both sides by 3 (to cancel fraction) : - 15 = n

You can check by plugging - 15 into the equation we made.