What trigonometric ratio could be used to find the
missing side? Tangent, Sine, or cosine?

cosine

Step-by-step explanation:

eliminate each ratio that will not work,

we'll just use Soh Cah Toa, which basically tells us when to use that ratio

Soh stands for sine=opposoite/hypotenuse

a sine ration would be the opposite side, but we are not given the opposite side, we are given the adjacent side, so we can eliminate this

Cah (correct answer)

Cah stands for cosine=adjacent/hypotenuse

x is the adjacent side to 27 degrees and we are given the hypotenuse, so this will work

Finally Toa won't work because

Toa stands for tangent=opposite/adjacent

We can automatically eliminate this because the tangent only uses the two legs, it does not use the hypotenuse

therefore our answer is the cosine ratio

feel free to ask any questions or comments, hope this helps