What is the formula to find the length of an arc when given the central angle and radius? can someone me with

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

Two angles are complementary. the larger angle is 36 more than the smaller angle. what is the measure of the larger angle?

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