IMO C

per question each can 3 1/2 cups i.e 7 serving for 1 can
for 60 servings 60/7 =8.5.... which is nothing but 9 cans

1 serving = 1/2 cup
60 serving = 30 cups

31/2 cups in 1 can
30 cups in 60/7 cans

which leads to 8. something so answer should be 9

IMO C

step 1 : 3*1/2 = 7/2
step 2: one serving needed for 1/2 cup, then 60 serving needs 60*1/2= 30 cups
step 3 : 1 can contain 7/2 cups

i.e 7/2 cups in one can

so 1 cup in {1/(7/2)=2/7} cans

and 30 cup in {2/7*30=60/7=8.5} can

so least no. of can required are 9 so ans. is C