Caharles can buy 50 oranges and 60 apples for $100. He can 100 oranges for $100. How many apples can he buy for $100?

"He can 100 oranges for $100" ---> each orange costs $1

"buy 50 oranges and 60 apples for $100" ---> 60 apples cost $50,
so for $100 he can buy 120 apples