First you need to set this problem up as a cross multiply fraction set (actually forgot the name of it so I described it as that).
10/15 * 30/x
Solve for X
450 = 10x
Simplify
45 = x
The Daily dose is 30 meq/45 ml. For a 30 day supply you just multiply by 30.
1350 ml is needed for a 30 day supply.