Question 1076470
Let a be for Andy, and b be for Brian. Then:
1/a + 1/b=1/72
Brian takes 17 more minutes than Andy, working alone so b=a+17. Then:
1/a + 1/a+17=1/72
72/a + 72/a+17=1
72(a+17)+72a=aČ+17a
aČ-127a-1224=0
(a+9)(a-136)=0
a=-9 or 136
Using the positive value, we get Andy's time working alone as 136 minutes, and Brians' time as 153 minutes. ☺☺☺☺