Answer:
30 weeks
Explanation:
Subtract 90 kilograms from 105 kilograms. (15 kilograms)
Convert 500 grams into kilograms. 500 grams is only half of 1000 grams which is the amount of grams you need to make up one kilogram, so we know we won't have a whole kilogram. You should come up with 0.5 grams as your answer once you have converted 500 grams into a kilogram.
Multiply 15 x 0.5 and you should get 30.
It will take Peter 30 weeks.