It’s 130°, because 50+50=100 and 2x is equal to the same angel on the direct opposite side so work where you have 50. then the 4 angles should add to 360° and 360-100= 260, then you have to divide 260 by 2 because it has to be equal to both side so then 260/2=130° and to know that it’s correct add 130+130+50+50 and you get 360°!
The board is 12x larger in length than the nails. (Since the width of the board and nails are unknown, I am assuming you mean the length, not area difference)
