Chapter 8.2, Problem 8.7P

A solution contains the following ions: ${\text{Na}}^{+}\left(\text{15 mEq/L}\right)\text{, }\left(\text{10}\text{. mEq/L}\right)\text{,}$ and ${\text{Ca}}^{+}\left(\text{2 mEq/L}\right)\text{.}$ If ${\text{CI}}^{-}$ is the only anion present in the solution, what is its concentration in $\text{mEq/L}$ ?