Let's get this math done. We have 3671 and 90 and we're going to add them all together.

Step 1: We'll start by adding the digits 1 & 0 in column 1 and get 1.

Step 2: We'll start by adding the digits 7 & 9 in column 2 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 6 & 0 in column 3 and get 7.

Step 4: We'll start by adding the digits 3 & 0 in column 4 and get 3.

So, 3671 + 90 = 3761.

