To find the x value...
First of all, we know that all angles in the triangle total up to 180 degrees.
Also, we know that because it is a right angle, there is a little square that means 90 degrees.
we are given one of the angles as 25 degrees
Let's make an equation to solve for the value x then the angle measure
3x + 11 + 25 + 90 = 180
combine like terms
3x + 126 = 180
subtract 126 from both sides to start isolating the variable x
3x = 54
now we will divide both sides by 3 to isolate the variable x
x = 18
Now we aren't done
plug in the value of x into the angle we have to solve for
3x + 11
3 ( 18) + 11
54 + 11
65
The missing angle measure is 65 degrees
Hope this helps :)