**Lesson Steps**:

There are two digits in both numbers. Let's start with the ones digit.

The ones digit of 21 is 1 and that of 35 is 5.

We add 1 and 5.

1+5= 6

We have the answer's ones digit.

There is no carry-over.

Next, we add the tens digits

Tens digit of 21 is 2, and that of 35 is 3.

We add 3 and 2.

3+2=5

Combining the tens digit and ones digit, we get the answer : 56.

**Answer**:

56

**Subject**: Math

**Topic**: Addition