Solution:

Choose the variables as follows:

g = amount of green solution

y = amount of yellow solution

r = amount of red solution

x = amount of radioactive solution

m = amount of mixed solution

and write the following equations. (We've numbered them so that we can refer to them more easily.)

We'll rewrite some of the above equations to make them more immediately useful.

Now we'll do a little algebra ....

Now we'll use equations 2 through 5 to solve for g, y, r, and x.