Question

It takes Franklin 14 hours to make a 200-square-foot cement

Answer 1

F = Franklin (rate) = 200 ft² / 14 hrs = 200/14 ft²/hr = 14.2587 ft²/hr
S = Scott (rate) = 200 ft² / 10 hrs = 200/10 ft²/hr = 20 ft²/hr

Combined . . .

Fx + Sx = 200

(F + S)x = 200

x = 200/(F + S)

(F + S) = 200/14 + 200/10 = 2000/140 + 2800/140 = 4800/140 = 240/7

x = 200/(240/7)

x = 200/240*7 = 20/24*7 = 140/24 = 35/6

x = 35/6 hrs = 5 5/6 hrs = 5 hrs 50 min