What related number sentence shows the commutative property addition 3+9=12

Can someone show me the steps to solve the problem?

Abacteria population is tripling every hour. by what factor does the population change in 1/2 hour? select all that apply

The triangle shown has a hypotenuse with a length of 13 feet. the measure of angle a is 20 degrees. and the measure of angle b is 70 degrees. which of the following is closest to the length, in feet, of line segment ac? no need to use a calculator to find the trig numbers. each function is listed below. 4.4 5 12.2 35.7