22. Introducing seawater into an empty reservoir, after the water evaporates, salt can be obtained. The salt content of seawater is $3.5 \%$, and the weight of water evaporated each day is the same after it is introduced into the reservoir. After 10 days, the salt content of the seawater becomes $5 \%$. After another $\qquad$ days, the salt content of the seawater becomes $12.5 \%$.
$14$