6+2=8 quarts of a new solution
0.45*6 - quarts antifreeze in a solution that is 45% antifreeze
0.19*2 - quarts antifreeze in a solution that is 19% antifreeze
x- concentration of a new solution
8x - quarts antifreeze in a new solution
0.45*6 + 0.19*2 = 8x
3.08=8x
x= 0.385 =38.5 %