Find the measure of the arc or angle indicated

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Uestion 1(multiple choice worth 5 points) (05.02)alex wants to paint one side of his skateboard ramp with glow-in-the-dark paint, but he needs to know how much area he is painting. calculate the area of the isosceles trapezoid. isosceles trapezoid with top base 12 feet, bottom base of 18 feet, and height of 6 feet. 72 ft2 84 ft2 90 ft2 108 ft2

Answer asap. you begin with 1/2 scoop of ice cream. since you're hungry, you ask the vendor for 2/7 more scoops of ice cream. then, you eat 5/8 scoops. how many scoops of ice cream are left on your cone? i will mark brainliest for first correct answer.