Question

A box contains 146 marbles which are either red or blue. there are 28 more blue marbles than red marbles. how many blue marbles are in the box?

Answer 1

R + b = 146.  Supposing that b=r+28, 

r + (r+28) = 146, or 2r + 28 = 146.

Simplifying:  2r = 118.  Then r = 59, and b = r+28 = 59+28 = 87 blue marbles