HELPPP ME WITH number 3 & “a” “b” “c”

An angle that measures between 90 and 180° is called a(,

Acyclist bike x distance at 10 miles per hour .and returns over the same path at 8 miles per hour.what is the cyclist average rate for the round trip in miles per hour ?

In the diagram below,abc is congruent to dec what is the value of x