Answer:
18 red marbles.
Explanation:
The complete question asks the probability of randomly drawing a red marble is 3/5?
Let x be the number of red marbles that must be added.
To find x we will do the following:
![(x+12)/(x+32) =(3)/(5)](https://img.qammunity.org/2020/formulas/mathematics/high-school/t94dbnvfxign2caaxt346d2ghk0xj1zyoa.png)
=>
![5(x+12)=3(x+32)](https://img.qammunity.org/2020/formulas/mathematics/high-school/7qjqggk9kn700ljyda547udud1fthr92lw.png)
=>
![5x+60=3x+96](https://img.qammunity.org/2020/formulas/mathematics/high-school/5s2zd187udlwskt0ozcihlvghdw5s9l2or.png)
=>
![2x=36](https://img.qammunity.org/2020/formulas/mathematics/middle-school/np2xprcsq996q6uwoo8lfciuvp7w27qsw1.png)
This gives x = 18
Hence, 18 red marbles will be added to the bag.