Let x be the number we are looking for.
Let us go statement by statement so we can find the inequality we want. First we are told "15 minus a number". That would be represented by the expression

now, this quantity should be "less than or equal to 8 times that number". So this translates to the expression

so if we put together these expressions, we get

To solve it, we first add x on both sides, so we get

If we operate on the right, we get

Now, we divide both sides by 9, so we get that

which is equivalent to

which mean that any number greater than or equal to 5/3 is a solution for this inequality