Answer:
The answer is 7/24.
Explanation:
I attached a picture, but I'll try to walk through it here.
1) A negative and a negative makes a positive, so h becomes positive.
2) I added 7/8 to both sides, in order to "isolate the variable", which simply means to get h by itself, on one side of the equation (you'll likely hear it said both ways).
3) I multiplied 7/8 by 3/3, and multiplied -7/12 by 2/2. This is known as a common denominator, which in this case is 24. You can only add and subtract fractions that have a common denominator.
4) Multiply both of the fractions to get 21/24 + (-14/24). "Adding a negative" is the same thing as subtracting.
5) 21 - 14 = 7, and since our denominators are the same, the answer is 7/24.
You can confirm the answer by substituting, or "plugging" 7/24 into your original equation, in place of h.