Lessons Fulfilling NCTM Standard 1a
Understand numbers, ways of representing numbers, relationships among numbers, and number systems

Abstract Algebra
2 videos by 1 teacher 
Adding / Subtracting Rational Expressions
11 videos by 2 teachers 
Adding Complex Numbers
4 videos by 1 teacher 
Adding Fractions
26 videos by 3 teachers 
Basic Inequalities
10 videos by 3 teachers 
Complex Fractions / Simplifying Rational Expressions
15 videos by 4 teachers 
Decimals
31 videos by 4 teachers 
Digits / Place Value
4 videos by 2 teachers 
Dividing Complex Numbers
4 videos by 2 teachers 
Dividing Fractions
13 videos by 6 teachers 
Division
10 videos by 3 teachers 
Equivalent Fractions / Reducing
17 videos by 8 teachers 
Intro to Fractions
14 videos by 5 teachers 
Introduction to Complex Numbers
6 videos by 2 teachers 
Least Common Multiple and Greatest Common Factor
11 videos by 4 teachers 
Length and Perimeter
16 videos by 4 teachers 
Matrices
8 videos by 3 teachers 
Mixed Numbers / Complex Fractions
12 videos by 5 teachers 
Multiplication
19 videos by 7 teachers 
Multiplying Complex Numbers
5 videos by 2 teachers 
Multiplying Fractions
14 videos by 7 teachers 
Numbers / Properties of Numbers
8 videos by 4 teachers 
Numbers and Estimates
7 videos by 4 teachers 
Order of Operations
20 videos by 6 teachers 
Pascal's Triangle
1 video by 1 teacher 
Percents
30 videos by 4 teachers 
Pi
1 video by 1 teacher 
Polynomial Equations
27 videos by 6 teachers 
Prime Factors
4 videos by 3 teachers 
Rational Exponents
6 videos by 2 teachers