# System for solving the King's problems

9 videos

6 skills

Whether in the real world or a cliche fantasy one, systems of equations are key to solving super-important issues like "the make-up of change in a troll's pocket" or "how can order the right amount of potato chips for a King's party." Join us as we cover (and practice with examples and exercises) all of the major ways of solving a system: graphically, elimination, and substitution. This tutorial will also help you think about when system might have no solution or an infinite number of solutions. Very, very exciting stuff!
If you want more examples, feel free to look at the other tutorials in this topic.
Common Core Standards: 8.EE.C.8, 8.EE.C.8a, 8.EE.C.8b, 8.EE.C.8c

### Trolls, tolls, and systems of equations

VIDEO
6:51 minutes

A troll forces us to use algebra to figure out the make-up of his currency. We end up setting up a system of equations

### Solving the troll riddle visually

VIDEO
5:41 minutes

Solving the system of equations visually. Now we can save the prince/princess

### Solving systems of equations graphically

VIDEO
2:22 minutes

Some practice solving systems graphically (exercises available at http://www.khanacademy.org/math/algebra/systems-of-eq-and-ineq/e/graphing_systems_of_equations )

### Graphing systems of equations

PRACTICE PROBLEMS

Graph a system of equations in slope-intercept or standard form

### King's cupcakes: Solving systems by elimination

VIDEO
9:00 minutes

Using simple elimination to figure out how many cupcakes are eaten by children and adults

### How many bags of potato chips do people eat?

VIDEO
9:21 minutes

Using elimination to solve a system of equations

### Simple elimination practice

VIDEO
4:18 minutes

Practice solving systems of equations through simple elimination (exercise at http://www.khanacademy.org/math/algebra/systems-of-eq-and-ineq/e/systems_of_equations_with_elimination_0.5 )

### Systems of equations with simple elimination

PRACTICE PROBLEMS

Solve systems of equation with one-step elimination (e.g., x-values or y-values cancel each other out).

### Systems with elimination practice

VIDEO
5:31 minutes

Example of solving systems of equations with elimination

### Systems of equations with elimination

PRACTICE PROBLEMS

Solving systems of equations with elimination.

### Talking bird solves systems with substitution

VIDEO
5:21 minutes

Solving systems of equations with substitution.

### Practice using substitution for systems

VIDEO
4:21 minutes

Example doing Khan Academy systems of equations exercise at: http://www.khanacademy.org/math/algebra/systems-of-eq-and-ineq/e/systems_of_equations_with_substitution

### Systems of equations with substitution

PRACTICE PROBLEMS

Solve systems of equations using substitution

### Systems of equations

PRACTICE PROBLEMS

Solve systems of equations with substitution and elimination.