The teacher taught me right. This is the "ten-point method" in the first grade mathematics: it means to circle 10 first, and then add the two outside the circle, which is 10+2= 12. The easiest way is to see 9 and think of 1.

Please read ten songs:

19 19 years of good friends,

Hand in hand,

3737 is so close,

Let's go together, four, four, six, six.

Make a pair of hands in half.

See 9 and think of 1,

See 8, think of 2,

Seeing 7 and thinking of 3,

See 6, think of 4.

See Osuka decimal.

Children should remember "9 to 1", "8 to 2", "7 to 3", "6 to 4" and "5 to 5"

The method of filling ten is simple and easy, and the thinking process includes "looking at a large number, dividing it by two, filling ten by three and adding four".