They had 17/12 ( 17 over 12, or 1 and 5 over 12) So the fractions have to have the same denominator. 12 is their common denominator. So: 3/4 = 9/12 2/3=8/12
Tina can finish in 5 hours Bill takes two hours longer than Tina. 5+2=7 Bill takes 7 hours to cut the lawn. 7+5=12 It takes both of them working together 12 hours. Hope this helped!