Answer:
x = 9
Explanation:
The sum of all the interior angles of a triangle = 180 degrees
one of the angles of the triangle's interior is blank, so to find it we can subtract the exterior angle measure next to it from 180 degrees (a straight line)
38 + (6x + 56) + (180 - (10x + 58)) = 180
Now, we can do our best to simplify and combine like terms:
[38 + 56 + (180 - 58)] + [6x - 10x] = 180
216 - 4x = 180
Now we can subtract 180 from both sides...
36 - 4x = 0
And then add 4x to both sides...
36 = 4x
Now we've manged to isolate x, all that's left is to divide both sides by 4
9 = x
Or
x = 9
Hope this explanation helped! Feel free to ask questions if anything didn't fully make sense!