The container that holds the water for the football team is 1/6 full. after pouring in 7 gallons of water, it is 1/2 full. how many gallons can the container hold?

Compare

1/6 to 1/2

to compare, make fractions same
1/2 times 3/3=3/6

1/6 added 7 gallons turns to 3/6
3/6-1/6=2/6
1/6+2/6=3/6
therfor 7 gallons=2/6=1/3
1/3 times 3/1=3/3=1

7 times 3/1=21

answer is 21 gallons