How much salt is in a mixture containing 10 gal of an 11% salt solution and 6 gal of a 7% salt solution

In a 10 gal of an 11% salt solution, 

11% of 10 gal are sal.

11% *10 gal=(11/100)*10 gal =0.11*10 gal = 0.1 gal is salt.

Similarly, 0.07*6 gal= 0.42 gal is salt of the 6 gal in the second solution.

The mixture is 10 gal +6 gal = 16 gal, and contains a total of

  0.1 gal +0.42 gal = 0.52 gal of salt.

0.52 = x% of 16

0.52=x%*16

x=(0.52/16)*100=0.0325*100=3.25

there is 0.52 gal of salt in the mixture, that is 3.25%