An amusement park line is moving about 4 feet every 15 minutes. at this rate, approximately how long will it take for a person at the back of the 50- foot line to reach the front of the line?

If the line is moving about 4 feet every 15 minutes, then a person will need about 3 hours to reach 50-foot line from the back to the front. It's because:

50 / 4 = 12,5 (that's how many quarters of an hour one needs to move 50 feet)
12,5 * 15 = 187,5 (that's how long it will take in minutes)

187,5 min = 3h 7min 30 sec

Approx. - 3h

Set it up in fractions and cross multiply:

15/4=x/50

4x=750

x=187.5 minutes which converts to 3.125

Your answer is 3 hours (: