Arc Length and Radians question- please help! Will mark brainliest! Is 20pts!

The answer is shown but please give me an explanation so I can show my work!

Which addition property is being illustrated below? (type commutative or associative) (6 + 7) + 1 = 6 + (7 + 1)

Segment xz is bisected by point y. if xy = 12x, and the measure of xz = 18x – 6, solve for x

The population of a small rural town in the year 2006 was 2,459. the population can be modeled by the function below, where f(x residents and t is the number of years elapsed since 2006. f(t) = 2,459(0.92)