Answer:
x = 6
<u><em>Sorry if this answer is not correct, if it is or is not, please tell me in the comments!</em></u>
Step-by-step explanation:
All of the angles add up to 180 degrees (since it is a triangle), so
(11x - 3) + (7x + 5) + (13x - 8) = 180
Then, combine the like terms.
31x - 6 = 180
Now, out goal is to separate the x from everything. To do that, we need to add 6 to 180.
31x = 186
Then divide by 31.
x = 6
(Feel free to replace x with 6 back in the previous equation to double check it!)