I buy 10 boxes of 10 Kg mangoes = 10 x 10 = 100 Kgs.
I buy 5 boxes of 10 Kg apples = 5 x 10 = 50 Kgs.
Total weight = 100 + 50 = 150 Kgs.
I consume 1/2 a Kg a day, therefore 150 Kgs will take me 300 days
(i.e, Day 1 I consume 1/2 a Kg, Day 2 I consume another half, 1/2 + 1/2 + 1 and so on...)
300 days = 300/7 weeks = 42 6/7 weeks.