Slower bike = X
Faster bike = X+9
They both ride for 2 hours, now you have 2x and 2(x+9)
The sum of the two cyclists is 66 miles:
2x +2(x+9) = 66
Use distributive property:
2x + 2x+18 = 66
Simplify:
4x +18 = 66
Subtract 18 from both sides:
4x = 48
Divide both sides by 4:
x = 48/4
x = 12
The slower bike was going 12 mi/h
The faster bike was 12+9 = 21 mi/h.
