What's the answer? why? how do i solve things like this?

Its C.
Triangle A is straight up and down and then when you rotate it 90 degrees at point C,It becomes point B.
To solve this, you basically just look at what point it is rotated at, then figure out how far it is rotated. 
Hope this helps :)

Byou start by adding them all and setting them equal to 180 since that is half of the total degrees in a circle.(2x+8) + (3x-14) + (3x-14) = 1808x-20 = 1808x = 200x = 25

X=y+4 is the answe