Question

find the length of the side labelled x in each of this triangle

Answer 1

If you are in class 11 or above, you'll easily understand it.
As you know, By properties of Triangles, (see the law in the above picture)
The 'k' is a constant.

For 1) a)
$\frac{4}{ \sin(85) } = \frac{b}{ \sin(65) } \\ b = \frac{4 \times \sin(65) }{ \sin(85) } \\ b = 3.639078942$
Similarly, you can do the rest of the parts.