CPM Homework Help : INT3 Problem 12-68

Mary has an antique marble collection containing $40$ marbles. She has five more red marbles than blue marbles and twice as many red marbles as green marbles. Write a system of equations to determine the number of each color of marble.

Hint:

Let $b =$ the number of blue marbles, $r =$ the number of red marbles,
and $g =$ the number of green marbles.

More Help:

$b + 5 = r$
$2g = r$
$r + g + b = 40$

More Help:

Solve the system of equations using a combination of substitution and elimination.