Junior one student speed:1/7.5 =10/75 = 2/15 Junior two student speed: 1/5.

2/ 15 * 1+ 1/5x = 1

2/ 15+ 1/5x= 1

1/5x= 13/ 15

x= 13/3

A: * * It takes 4 hours and 20 minutes.