PLZ HELP ILL MARK U BRAINLIEST

△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 .

I'll give brainliest if you answer right : )

How do you use the elimination method for this question? explain, because i really want to understand!