Mr Sahota can harvest an acre of maize in half the time it takes him to harvest an acre of millet. To harvest 3 acres of each crop takes him a total of 6 days. How long would it take him in total to harvest 5 acres of maize and 2 acres of millet?
I think the key 'insight' they're looking for here is that if Mr Sahota can harvest an acre of maize in half
the time it takes him to harvest an acre of millet, then of the total 6 days he spends harvesting, 1/3 of that time (i.e. 2 days) must be spent harvesting maize and 2/3 of that time (i.e. 4 days) must be spent harvesting millet.
Given that within that 6 days he harvested 3 acres of each crop, he harvests maize at a rate of 3 acres per 2 days (1.5 acres per day) and millet at 3 acres per 4 days (0.75 acres per day).
We then just need to multiply each 'acres per day' by the number of acres in the question.