On average, jenny does five loads of washing per week. she buys a 1.2k box of kapow! laundry powder. and can only use 60g a load

how many weeks should the box of powder last for jenny?

Given:
5 loads of washing per week
1.2kg box of laundry detergent 
60 g per load.

convert 1.2 kg to grams.
1 kg = 1000 grams

1.2 kg * 1,000g/1kg = 1,200 g
1,200 g / 60 g per load = 20 loads
20 loads / 5 loads per week = 4 weeks

It would take 4 weeks for a 1.2 kg box of Kapow! laundry powder to last.