Common Core
1.NBT.B.2.b
3 lessons teach this standard. Every lesson is interactive, and every one prints as a worksheet with a separate answer key.
Grade 1 Math · Chapter 4 · Lesson 2
Every teen number is a ten with a few left over.
Grade 1 Math · Chapter 4 · Lesson 3
Thirteen is really "ten three".
Grade 1 Math · Chapter 4 · Lesson 5
Split a teen number into ten and the rest.