SOH CAH TOA tells you
Sin(x) = Opposite/Hypotenuse
The side opposite x is 9; the hypotenuse is 15.2. Putting these values into the above equation gives you the second selection
sin(x) = 9/15.2
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SOH CAH TOA is a mnemonic that can be used to remember the definitions of the basic trig functions, sine, cosine, and tangent. In this context, A stands for the side Adjacent to the angle.