Problem
Simplify. \[ \frac{5^{2}+2^{2}-1^{2}}{8 \div 2 \cdot 9 \cdot 1 \div 9} \] Select the correct choice below and, if necessary, fill in the answer box to complete your choic A. $\frac{5^{2}+2^{2}-1^{2}}{8 \div 2 \cdot 9 \cdot 1 \div 9}=$ B. The expression is undefined.
Solution
Step 1 ：Simplify the numerator: \(5^{2}+2^{2}-1^{2} = 25+4-1 = 28\)
Step 2 ：Simplify the denominator: \(8 \div 2 \cdot 9 \cdot 1 \div 9 = 4 \cdot 9 \cdot 1 \div 9 = 4\)
Step 3 ：Divide the numerator by the denominator: \(\frac{28}{4} = 7\)
Step 4 ：Final Answer: \(\boxed{7}\)
