Question

There are 765 marbles in a box. There are twice as many blue marbles as green marbles. There are three times as many red marbles as blue. How many blue marbles are there in the box?

Answer 1

B=blue
g=green
r=red
2 times as many blue as green
b=2g
3 times as many red as blue
r=3b
subsitute 2g for b
r=3(2g)=6g
r=6g

r+g+b=765
so we subsitute
r=6g
g=g
b=2g

6g+g+2g=765
add like terms
9g=765
divide both sides by 9
g=85
subsitute
b=2b
b=2(85)
b=170

170 blue