NBT.1.1

Composes and decomposes numbers from 11 to 19 into 10 ones and some further ones (e.g., by using objects or drawings) and records each composition or decomposition by a drawing or equation (e.g., 18 = 10 + 8); understands that these numbers are composed of 10 ones and one, two, three, four, five, six, seven, eight, or nine ones.