K.NBT. Kindergarten - Number and Operations in Base Ten
K.NBT.A. Work with numbers 11--19 to gain foundations for place value.
K.NBT.A.1. Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (e.g., 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.