Khan Academy: Algebra: Find an Unknown Proportion 2

Video demonstrates how to find an unknown in a proportion three different ways including algebraically with cross multiplication. This video also appears in the strand Arithmetic and Pre-Algebra: Ratios and Proportions. [7:20]

This video demonstrates how to evaluate an expression with two variables using substitution. [1:46]

Video demonstrates how to divide by a monomial to find the height of a cylinder with a given volume and radius. [4:05]

Video shows an example of finding asymptotes of a rational function. Uses the asymptotes and the behavior near the asymptotes to graph the function. Includes an example of a rational function that does not have asymptotes. [8:20]

A short video with an explanation on how to find a unit price from a real-world application problem. This video also appears in the strand Arithmetic and Pre-Algebra: Ratios and Proportions. [2:01]

This lesson goes through three examples of matrix multiplication. Explains how the dimensions of matrices affect whether or not the matrices can be multiplied, how to determine if they can be multiplied, and what size the resulting...

This video demonstrates how to set up and solve a system of equations in order to solve a word problem concerning rates. [10:04]

A video that demonstrates how to set up and solve systems of equations in order to answer word problems. [12:20]

A continuation of the video Limit Examples (Part 1), also from the Khan Academy. Addresses the case where the limit of a function is equal to infinity. Examples are explained both graphically and tabularly. [6:58]

This video shows how to find an unknown quantity in a proportion in the context of a word problem. Practice problems are available. [5:48]