Which trigonometric function will correctly solve for side AC?

If the scale factor between two circles is 2x/5y what is the ratio of their areas?

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

Measure a and b and find their sum. how are the angles related?