Find bc. Round the answer to the nearest tenth.

Is BC=2.3 one of the options?

For that question, you can use the cosine rule, where;
[tex]{a}^{2} = {b}^{2} + {c}^{2} - 2(b)(c) \cos( \alpha ) [/tex]
In this case, we have..
[tex] {bc}^{2} = {1.8}^{2} + {2.1}^{2} - 2(1.8)(2.1) \cos(70) [/tex]
Solving for BC with this will get you 2.250406, rounded off to the tenth is 2.3.