Strategy 1 - Break down into 1s and 10s:

1. First add the numbers in the ones place (shown in green)

2. Next add the numbers in the tens place (shown in blue)

Strategy 2 - Using a number line

1. Start by writing down the larger number at the right side of the number line

2. Subtract by skipping by 10s, 5s, or 1s (in the example, 23 is broken down to two 10s and three 1s)