Algebra-2

The missing number is 7.

 

In Pascal's Triangle, every number (except the 1s on the leftmost and rightmost positions of each row) is the sum of the two numbers directly above it in the previous row.

 

For the eighth row where the missing number is located, we look at the seventh row which consists of 1, 6, 15, 20, 15, 6, 1.

 

The number we are trying to find in the eighth row has the two numbers 6 and 1 directly above it from the seventh row. When we add 6 and 1 together (6 + 1), we get 7.

 

So the completed Pascal's Triangle would be:

                    1

            ...