Abag is filled with blue and green marbles. there are three rimes as many blues as green ones. if the bag contains 280 marbles total. how many blue ones are there?

Let b represent blue marbles
g represent green marbles
Then,
We know that there are three times as many blues as green ones, so
b=3g
Next,
the bag contains 280 marbles total, so:
b+g=280 marbles
Substitute b=3g into this equation, to get
3g+g=280 marbles
4g=280 marbles
Divided 4 to each side
4g/4=280/4
g=70 marbles
b=3r
b=3(70)
b=210 marbles
Check:
b=3r
210=3(70)
210=210
b+g=280
210+70=280
280=280. As a result, there area 210 blue marbles. Hope it help!