Stuck on this problem, help would be appreciated

Abcd is a parallelogram find the valuse of x

Asequence is defined recursively by the formula  f(n  +  1)  =  f(n)  +  3 . the first term of the sequence is  –4. what is the next term in the sequence? –7–117

Which triangle congruence postulate or theorem justifies my claim that the steps i made using construction paper and scissors produce an isosceles triangle? was it sss, sas, asa, aas, or hl?