Grade 2 Term 1 Big Idea:
Numbers to 100 represent quantities that can be decomposed into 10s and 1s
Vocabulary:  add/subtract, sum, difference, compose, decompose

Number bonds for decomposing number into 10s and 1s and vice versa               

Grade 3 Term 1 Big Idea:
Development of computational fluency in addition and subtraction of whole numbers requires flexible decomposing and composing
Vocabulary:  add/subtract, sum, difference, compose, decompose, place value terms

a) Number bonds for decomposing a number into hundreds, tens and ones
b) Anchor chart showing place value representation of a number
     

References:
Adding & Subtracting Double Digits with Regrouping
   

Video:  Subtraction with Regrouping

 Vocabulary:  digit, add, subtract, sum, difference, compose & decompose, addend & minuend