x=-3
Explanation:
To start off, you're going to want to know and understand that all the angles of triangle equal 180 degrees.
Now that we know a triangle equals 180 degrees, lets make an equation. This is equation can be 55+54+74+x=180.
Now, lets combine the like terms in the equation. The equation now becomes 183+x=180.
From here, we subtract 180 from both sides, which would get us x=-3.
To double check that this is correct and that it works, you can plug in the -3 where the x would be.
I hope this helped!! Let me know if you have any further questions.