The three angles of a triangle add up to 180 degrees. Let's call the third angle y:
53 + 45 + y = 180 Subtract 98 from each side
y = 82
The third angle is equal to 82. We also know that the two angles, x and y, will add up to 180 degrees.
x + y = 180 Plug in 82 for y
x + 82 = 180
x = 98 degrees