Problem:
Some marbles in a bag are red and the rest are blue. If one red marble is removed, then one-seventh of the remaining marbles are red. If two blue marbles are removed instead of one red, then one-fifth of the remaining marbles are red. How many marbles were in the bag originally?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
Let be the number of red marbles and the total number of marbles originally in the bag.
Then
Solve and simultaneously to find .