Question

Please help! What are the variables??

Answer 1

variables are all letters like b, c, d, v....

Answer 2

I guess the next question is how to solve, right?

Answer 3

Yes :)

Answer 4

what happened?..

Answer 5

Using parallelogram properties, you have
\(\angle A = \angle C\) which is b-10 =d
\(\angle B = \angle D\) which is b+10 =c
\(\angle A + \angle B+\angle C+ \angle D =360\)
which is b-10+d +b+10+c =360 or 2b+c+d =360
solve the system .

Answer 6

Ok I think I've got it from here. Thank you so much for your help, really appreciated!