Evaluate ${ }_{9} C_{2}$

Step 1 ：The problem is asking for the combination of 9 items taken 2 at a time.

Step 2 ：The formula for combination is given by: \(C(n, r) = \frac{n!}{r!(n-r)!}\) where n is the total number of items, r is the number of items to choose, and ! denotes factorial. In this case, n=9 and r=2.

Step 3 ：Substituting the values into the formula, we get \(C(9, 2) = \frac{9!}{2!(9-2)!}\)

Step 4 ：Solving the above expression, we get the combination as 36.

Step 5 ：So, the combination of 9 items taken 2 at a time is \(\boxed{36}\).