Hello!
When you are given the value of a variable, to solve an equation with it, all you need to do is take the value a variable is assigned, and substitute that in the equation. In this case, we are given that h is 8, so we can substitute h in for each case we see "h" in the equation.
6h therefore can become 6 (8). Note that 6h = 6 * h, and 6(8) = 6 * 8.
Now, just solve. 6 * 8 = 48.
Therefore, your final answer is 48.
Hope this helps!