can yall help me? 30 points to the first 2 reply with the right answer and ill make you brainist or whatever but only to one person that have the right answer!

In the proof of the triangle angle sum theorem, you must draw an auxiliary line. which construction must you use to draw this line?

△cde maps to △stu with the transformations (x, y) arrowright (x − 2, y − 2) arrowright (3x, 3y) arrowright (x, −y). if cd = a + 1, de = 2a − 1, st = 2b + 3 and tu = b + 6, find the values of a and b. the value of a is and the value of b is .

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