Tell how the Commutative and Associative Properties of Addition can help you evaluate the expression. 8.5+3.4-6.5-(-1.6) Also whats the answer

How many liters of peroxide should be added to 12 liters of an 8% peroxide solution so that the resulting solution contains 16% peroxide?   original added new amount of peroxide 0.96 liters x 0.96 + x amount of solution 12 liters x 12 + x 0.18 liter 1.14 liters 1.92 liters 2.10 liters