We are presented with 715 and 84. Let's work out the sum.

Step 1: We'll start by adding the digits 5 & 4 in column 1 and get 9.

Step 2: We'll start by adding the digits 1 & 8 in column 2 and get 9.

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

So, 715 + 84 = 799.

