Hello there! We can solve this by writing and solving an equation. Set it up like this:
3x + 5 = 4x - 45
Setting it up like this will get us to the value of "x", because those equations equal each other and the lengths of those angles are equal. First, let's subtract 3x from both sides to get 5 = 1x - 45. Now, add 45 to both sides to get 50 = 1x. Divide each side by 1 to isolate the "x". 50/1 is 50. Let's plug the value in and see if it works. 3 * 50 is 150. 150 + 5 is 155. 4 * 50 is 200. 200 - 45 is 155. 155 = 155. There. x = 50.