Khan Academy
Khan Academy: Add & Subtract Mixed Numbers With Unlike Denominators (Regrouping)
Practice adding and subtracting mixed numbers with different denominators. Regrouping required.
Shmoop University
Shmoop: Fractions & Decimals: Adding & Subtracting Decimals
The mathematics notes investigate how to add and subtract decimals. Examples and practice problems with solutions are included.
Khan Academy
Khan Academy: Adding & Subtracting Rational Numbers
Practice adding and subtracting rational numbers of different forms.