In δabc, if a = c = 16 centimeters and m∠b = 85°, what is b to two decimal places?

The length of side b may be calculated through the Cosine Law. Which can be mathematically expressed as,
                               b² = a² + c² - 2ac(cos B)
Substituting the given values,
                               b² = (16 cm)² + (16 cm)² - 2(16 cm)(16 cm)(cos 85°) 
                                            b = 21.6189 cm
Thus, the value of b in two decimal places is approximately 21.62 cm. 

It’s 24.6 after you round to the nearest tenths the answer should be 25.0

Is it multiple choice