math algebra
posted by bob .
how would i do this problem elina and teresa raced on their bikes to the library after school. they both left at 3:00 pm and bicycled along the same trail elina rode at the speed of 12 miles an hour and teresa rode at the speed of 9 mph. elina got there 15minutes before teresa at wat time did elina get to the library

Let x=distance from library
x/9x/12 = 0.25 (15 minutes)
Solve for x.