This is because if for every $50 he saves $5, and he has saved a total of $500, you can set up a proportion to find out how much money he has saved at that point.
The proportion is as follows:
50/5 == 500/x
x is equivalent to the amount of money he has saved
You can cross multiply to get the following equation:
50x == 2500
To isolate x, you must divide both sides by 50, giving you an answer of:
Add 35+ 72.5=107.5 that should give you your answer for c and the answer for d is acute because the triangle would have to be 360 to be Obtused and it's not a right triangle because you don't have a 90 degree angle