Hi, my final answer for this triangle is 28.88. am i doing something wrong?

What's the question- what is x?
So for this triangle, since it's not right (No 90° angle, at least not shown), we must use special trigonometric triangles. You may have used Pythagorean Theorem, but you can't unless it's a right triangle.
Now we decide between Law of Sines vs. Law of Cosines. L. of Sines is for when we have 2 angles and one or more sides. L. of Cosines is for when we don't have that 2nd angle, but do have 2 sides... our case here.
Here's how the Law of Cosines works:

where c is the side needed, a & b are the 2 known sides, and gamma (γ) is the angle opposite the side c.
So a = 21, b = 42, γ = 39°




NOPE YOU DID IT CORRECTLY!!

You're "x" = 28.88°

Definitely