Carson Dellosa Education & Spectrum 
Subtraction, Grade 1 [PDF ebook] 

Subtraction skills are a necessary building block to create solid math proficiency. Spectrum Subtraction for grade 1 provides standards-based practice to help children use visual models to represent problems, understand unknown number equations, and strengthen place value strategies. This comprehensive workbook elevates math readiness and establishes a strong foundation for more complex math concepts. Mastering math is a long process-start with the basics. With the help of this best-selling series, Spectrum Subtraction guides children through the beginning stages so your child will develop early math skills through practice and activities that strengthen their understanding of when, why, and how to use subtraction and other grade-specific math concepts.