Respuesta :
Answer:
12 red marbles
Step-by-step explanation:
You make an equation: 3x+4x=21
Then, you get 7x=21.
By using algebra, you get x=3.
Then you muliply 3 by 4 since the ratio of red marbles is 4.
So you get 12.
Answer:
There are 12 red marbles
Step-by-step explanation:
green : red : total
3 4 3+4=7
We want a total of 21
21 /7 =3
Multiply by 3
green : red : total
3*3 4*3 7*3
9 12 21