Fluently Add and Subtract Within 20 - 2nd Grade Math

$6$. Half of 12 is 6.

$3$. Count back 7 from 10 to get 3.

$15$. Think of 8 + 8 = 16, then subtract 1.

$18$. Double 9 equals 18.

$11$. Make 10: 3 + 7 = 10, then add 1 more.

$16$. Double 8 equals 16.

$12$. Double 6 equals 12.

$9$. Zero plus any number equals that number.

$7$. Adding zero to any number gives the same number.

$9$. 19 minus 10 equals 9.

$8$. Count back 7 from 15 to get 8.

$8$. 13 take away 5 leaves 8.

$9$. Half of 18 is 9.

$7$. Count back 4 from 11 to get 7.