The little square means 90° and a straight line means 180° so 180 minus 68° minus 90° is 22° which leaves, 1) 112° and since you can flip 68° exacly the same on both sides it is a vertical angle which means 3)68. 4) 90°
Try sketching the cardboard piece labeling each side. when folded, the height of the box is x, the length is now (13 - 2x), the width is now (6 - 2x) after cutting out the squares from each corner.
