Memorize Subtraction Facts

(D) Apply basic fact strategies to add and subtract within 20, including making 10 and decomposing a number leading to a 10

(Y1) Represent and solve simple addition and subtraction problems using a range of strategies including counting on, partitioning and rearranging parts (ACMNA015)

K.OA.5 Fluently add and subtract within 5.

2.OA.2 Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.