Question 315624
in some time (t), Jack will mow t/3 of the lawn
___ during the same time, Marilyn will mow t/7 of the lawn
___ these two fractions add up to the whole lawn


(t/3) + (t/7) = 1


multiplying by 21 (LCD) ___ 7t + 3t = 21


10t = 21 ___ t = 2.1