Find the missing number.
6 + _____ = 4 + 6

The correct answer is: 4

Here, we can observe an equal sign which shows that the value on the left is the same as the value on the right.
4 + 6 = 10
and 6 + ___ = 10
10 - 6 = 4
So, the missing number is 4.
So, correct choice is 1.