Lawrence Hall of Science
The Math Page: Skill in Arithmetic: The Meaning of Subtraction, and Mental Calculation
This website explains and defines basic subtraction. There are practice problems at the very end of this lesson.
Homeschool Math
Homeschool Math: Adding and Subtracting Decimals With Two Decimal Digits
This is a complete lesson with instruction, word problems, and exercises about adding and subtracting decimals with two decimal digits (hundredths).
CK-12 Foundation
Ck 12: Elem Math: Adding and Subtracting Three or More Numbers
[Free Registration/Login may be required to access all resource tools.] This is a set of practice problems where students are given word problems where they have to add or subtract 3 or more 1-digit numbers.