ANSWER:
31.2
STEP-BY-STEP EXPLANATION:
The first thing is to recreate the QRS triangle to better understand the question:
We can calculate the length of RS, by means of the cosine law, which is the following:
[tex]c^2=a^2+b^2-2\cdot a\cdot b\cdot\cos C^{}[/tex]
In this case then it would be:
[tex]\begin{gathered} RS^2=QR^2+QS^2-2\cdot QR\cdot QS\cdot\cos Q \\ \text{ Replacing} \\ RS^2=21^2+30^2-2\cdot21\cdot30\cdot\cos 73 \\ RS^2=441+900-1260\cdot\cos 73 \\ RS^2=1341-368.39 \\ RS=\sqrt[]{1341-368.39} \\ RS=31.2 \end{gathered}[/tex]
The value of RS is equal to 31.2
