Need help on 13 &14 please

Acircle has a circumference of 28.36 units what is the diameter of the circle

Select the correct answer from each drop-down menu. a system of equations and its solution are given below. system a complete the sentences to explain what steps were followed to obtain the system of equations below. system b to get system b, the equation in system a was replaced by the sum of that equation and times the equation. the solution to system b the same as the solution to system a.]

Divide. –40 ÷ –5 a –8 b 200 c -200 d 8