What do I do for this problem?

Answer:
6.9 feet to the nearest tenth.
Step-by-step explanation:
You use the Cosine Rule:
XZ^2 = 12^2 + 10^2 - 2.12.10 cos 35.1
= 144 + 100 - 240 cos 35.1
= 47.644
XZ = √47.644
= 6.90.