Question

There are 27 red or blue marbles in a bag.The number of red marbles is 5 less than 3 times the number of blue marbles. How many red marbles are in the bag? How many blue marbles are in the bag?

Answer 1

b= # of blue marbles
r= # of red marbles

r+b=27
r=3b-5

3b-5+b=27
4b-5=27
4b=32
b=8

r=3(8)-5
r=24-5
r=19

there are 8 blue marbles and 19 red

Answer 2

r=red
b=blue

r+b=27

r=3b-5
subsitute 3b-5 for r in r+b=27
3b-5+b=27
4b-5=27
add 5 to both sides
4b=32
divide both sides by 4
b=8

plug 8 for b in r+b=27
r+8=27
subtract 8 from both sides
r=19

b=8
r=19