1, break the ten method: add nine MINUS one, add eight MINUS two, add seven MINUS three, add six MINUS four, and add five to see five.

2. Digital splitting method: 9+6 = 9+(1+5) = (9+1)+5 =15.

3. Make up ten songs: 19 19 Good friend, 2828 holding hands, 3737 really close, 4646 walking together, 55 making up one hand. One plus nine, ten tadpoles, two plus eight, ten old ducks, three plus seven, ten old hens, four plus six, ten golden monkeys, five plus five, and ten big tigers.

4.20 Carry-in addition: Look at large numbers, divide them into decimals, make up ten, and add the remainder.

5, abdication subtraction: see 0, go forward and see which one has it. Borrowed and walked back, 0 is a bit like 9.