Answer:
You have 24 blue marbles.
Explanation:
We can solve this question by a system of equations.
I am going to say that:
x is the number of red marbles.
y is the number of blue marbles.
28 red and blue marbles
This means that
![x + y = 28](https://img.qammunity.org/2019/formulas/mathematics/college/wmcyzqc9sba4jyclv38fnv7pg5m8eti75z.png)
The ratio of red to blue is 1:6.
This means that for each red marble(x), we have 6 blue marbles(y). So
y = 6x.
Then
![x + y = 28](https://img.qammunity.org/2019/formulas/mathematics/college/wmcyzqc9sba4jyclv38fnv7pg5m8eti75z.png)
![x + 6x = 28](https://img.qammunity.org/2019/formulas/mathematics/high-school/15gn943isvh7dqt84u7iewqici1lrgcjbu.png)
![7x = 28](https://img.qammunity.org/2019/formulas/mathematics/high-school/y58zb147q1ia0w1wkpfl649hzu35r9ea7i.png)
![x = 4](https://img.qammunity.org/2019/formulas/mathematics/high-school/atvjgwdx0v4qkei0dce4beeina444xt06p.png)
We want the number of blue marbles(y)
![x + y = 28](https://img.qammunity.org/2019/formulas/mathematics/college/wmcyzqc9sba4jyclv38fnv7pg5m8eti75z.png)
![4 + y = 28](https://img.qammunity.org/2019/formulas/mathematics/high-school/spwmmkbfuxhtywr4szepee10to0h7rfyo2.png)
![y = 24](https://img.qammunity.org/2019/formulas/mathematics/middle-school/lli1tsvg0lypmyeq7y7jvemb6u0q5oawce.png)
You have 24 blue marbles.