Glenora

A box with 40 stuffed animals in it weighs 350 ounces. The same box with 30 stuffed animals weighs 290 ounces. How much does the box itself weigh?

A jar contained 50 marbles. Of the 50 marbles, 90% of them were red and the remainder were green. Some of the red marbles were removed from the jar and after this, 75% of the marbles in the jar were red. How many red marbles were removed from the jar?