Answer:
13.3
Step-by-step explanation:
[tex] a^2 = b^2 + c^2 - 2bc \cos A [/tex]
[tex] a^2 = 8^2 + 18^2 - 2(8)(18) \cos 43^\circ [/tex]
[tex] a^2 = 64 + 324 - 288(0.73135) [/tex]
[tex] a^2 = 388 - 210.6299 [/tex]
[tex] a^2 = 177.370 [/tex]
[tex] a = \sqrt{177.370} [/tex]
[tex] a = 13.318 [/tex]
Answer: 13.3
