Your mom's
garden watering
barrel had 12
gallons of water
in it. while
raining, it fills up
with 5 gallons of
water every
hour.

If you wanted to write an equation it would be:

12 + 5h = g

-h representing the hours

-g representing gallons of water

(you don't have to use those variables, just for a reference)

So if you want to know how many gallons there would be after a certain number of hours, just plug the number in where h is and solve.

Example:

10 hours

12 + 5(10) = g

12 + 50 = g

g = 62

62 gallons of water after 10 hours