hans and greta live 21 miles apart at 1pm they start riding

hans and greta live 21 miles apart. at 1pm they start riding their bikes towards each other and meet at 1:45pm. if greta\'s average speed is 4 miles per hour faster than hans\' average speed. find gretas average speed

Solution

They travel 21 miles in 0.75 hours (45 minutes) so their combined speed is
28 mph. Their speeds are added going in opposite directions.
g + h = 28 (sum of speeds)
g = h + 4 (greta\'s speed is 4 more than that of hans)
Sub for g into the 1st eqn
(h+4) + h = 28
2h + 4 = 28
2h = 24
h = 12 mph
------
g = 16 mph