Two bicyclist ride in opposite directions. The speed of the first bicyclist is 5 miles per hour faster than the second. After 2 hours they are 70 miles apart. Find their rates.
f = s + 5
2 (f + s) = 70
substituting ... 2 (s + 5 + s) = 70 ... 4 s + 10 = 70
solve for s , then substitute back to find f