Question

Every week, nina used 5 l of water from her rain barrel to water her plants. she did this until her rain barrel was empty. when nina first started watering, her rain barrel contained 75 l of water.

Answer 1

Assuming that you wanted to find out how long Nina's has been doing her watering activities, you should just simply divide the total amount of barrel with its daily usage.

75 / 5 = 15 weeks

hope this helps