The value of x is 16
The measure of the missing angle is 48
This is because it’s a right angle meaning the two angles HAVE to equal 90.
You can set the equation as
42 + 3x=90
3x= 48 (subtract 48 by 90)
X=16 (divide both sides by 3)
And then you can plug 16 back into the 3x which would be 3(16) which equals 48
Or
You can set the equation as
90-42= 48
And divide by 3 to get x=16