When adding fractions, you want the denominators to be the same number, so you have to multiply 31/2 by four for the numerator and denominator by 4 to have the denominators to both be 8. So the fraction on the left will be 124/8 + 1/8 =129/8. That fraction is in its simplest form.
The solution comes rom the formula for finding the slope of a graph: Rise/Run
In this case, the rise would be -2, because it is going down the graph 2 points. The run would be 5, because it is going to the right 5 points. Hopefully this will help you in the future.
the answer is 84 being how you asked the question but I dont think thats what you meant to ask. if thars wrong just tell me and ill answer it the way you need it