This video from Maths Explained will show you how to simplify some basic algebraic expressions involving addition, subtraction, multiplication and division (8 m, 30 s)
Examples in this video from The Organic Chemistry Tutor include the area of a trapezoid formula, ohm's law with voltage current and resistance. (15 m, 23)
This video from the Organic Chemistry Tutor explains how to solve inequalities that contain fractions and variables on both sides including absolute value function expressions. (30 m, 43 s)