Find the Missing Operator in 63-51□88-42: Mathematical Expression Challenge

To solve this problem, we'll follow these steps:

• Step 1: Calculate $63 - 51$.
• Step 2: Calculate $88 - 42$.
• Step 3: Compare the two results and choose the correct sign.

Now, let's work through each step:

Step 1: Calculate $63 - 51$.
$63 - 51 = 12$.

Step 2: Calculate $88 - 42$.
$88 - 42 = 46$.

Step 3: Compare the results of Step 1 and Step 2.
We have $12$ and $46$.

Since $12$ is less than $46$, we use the sign $<$ to complete the inequality.

Therefore, the correct inequality is $63 - 51 < 88 - 42$.

The solution, therefore, is $<$.