Answer
$A \approx 28^o$
Work Step by Step
RECALL:
In a right triangle,
$\sin{A} = \dfrac{\text{length of opposite side}}{\text{length of hypotenuse}}
\\\cos{A} = \dfrac{\text{length of adjacent side}}{\text{length of hypotenuse}}
\\\tan{A} = \dfrac{\text{length of opposite side}}{\text{length of adjacent side}}$
Use the cosine formula to obtain:
$\cos{A} = \dfrac{\text{length of adjacent side}}{\text{length of hypotenuse}}
\\\cos{A}=\dfrac{15}{17}$
Use the inverse cosine function of a scientific calculator to obtain:
$A = \cos^{-1}{\frac{15}{17}}
\\A = 28.07248694^o
\\A \approx 28^o$