An athlete's speed on her bike is 14mph faster than her average speed running. She can bike 31.5 miles in the same time that it takes her to run 10.5 miles. Find her average speed running and her average speed biking.
you would cross multiply. 14 over 31.5 and X over 10.5 10.5 times 14 is 147 divide that by 31.5 which is 4 1/3 and that is how fast she can run 4 1/3 mph