A mixture of
14
%
14
%
disinfectant solution is to be made from
12
%
12
%
and
17
%
17
%
disinfectant solutions. How much of each solution should be used if
10
10
gallons of the
14
%
14
%
solution are needed?

Its a bit hard to read your question but it looks like its a mixture of 12% and 17% solutions forming a 14% solution.
This is essentially like a molarity question. The total volume must be ten, and the average the %s must be 14.

The answer is 4 gallons of 17% and 6 gallons of 12%