3.5:
https://www.youtube.com/watch?v=yi9Fq0mo1Hs
https://www.youtube.com/watch?v=9MLWTNwsPeo
3.6 In Class: 'Bring You Calculator to School Day..'
3.7 Formulas
https://www.youtube.com/watch?v=75y_tRvBtOE
https://www.youtube.com/watch?v=-5poaAB9piQ
3.8 Ratios and Rates
https://www.youtube.com/watch?v=t_qZfSVHNHQ
https://www.youtube.com/watch?v=AOci-hojRKg