Answer:
104
Explanation:
All interior angles of triangles add up to 180. So, using the information we are given we can find the missing angle, theta. One way to do this by setting up an equation like 31+45+θ=180. Solve this to get 104, your final answer. If you want, you can check your work by plugging in 104, 31+45+104=180. Since 180=180, 104 must be correct.