Question 835081
earlier
40x+60(1+x)=240
40x+60+60x=240
100x+60=240
100x=180
x=1.8 hours at 40 and 2.8 hours at 60
later
40x+60(x-1)=240
40x-60+60x=240
100x-60=240
100x=300
x=3 hours at 40=120
x-1 =2 hours at 60=120