All three angles in a triangle add up to 180 degrees.
Therefore, we should just add up all the angles given to us and set them equal to 180 :)
3x + 5x + (2x + 5) = 180
Now we just need to combine all the similar terms together (which is the 3x, 5x, and 2x):
10x + 5 = 180
Subtract 5 from both sides of the equation:
10x = 175
Now just divide by 10 on both sides to isolate the x and work out your value:
x = 17.5
Therefore, your final value of x is 17.5 :)