To calculate the size of the angle marked Y, we can use the law of sines or the law of cosines. Using the law of sines, we can solve for y by using the following equation:
sin(y) = opposite/hypotenuse
Where opposite is the length of the side that is next to the angle Y, and hypotenuse is the length of the longest side of the triangle. For the purposes of this question, the opposite is 80° and the longest side is 145°. Therefore, the size of the angle marked y is 49°.