Ratios and Equivalent Ratios
https://www.khanacademy.org/math/cc-sixth-grade-math/cc-6th-ratios-prop-topic/cc-6th-ratios-intro/v/ratios-intro
Solving Proportions using algebraic equations (CMD = Cross Multiply and Divide)
Converting Customary and Metric Measurement using proportions:
Ratios in Tables: