So if you write this out, you get:
the difference of x and 8: x - 8
is less than or equal to: ≤
20
so,
x - 8 ≤ 20.
To solve this, you can just treat this like a normal equation, as long as you aren't dividing or multiplying by a negative number.
x - 8 + 8 ≤ 20 + 8
x ≤ 28
