Useful Math Links
https://www.khanacademy.org/math
http://www.mathplayground.com/index_multiplication_division.html
http://www.virtualnerd.com/algebra-1/linear-equation-analysis/slope-rate-of-change/understanding-slope/slope-definition
http://www.virtualnerd.com/algebra-1/linear-equation-analysis/slope-rate-of-change/slope-examples/slope-from-graph
http://www.virtualnerd.com/algebra-1/linear-equation-analysis/slope-rate-of-change/understanding-slope/rate-of-change-two-points-graph