# Introduction to systems of equations

9 videos

5 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". This tutorial shows you how to solve systems of equations graphically.

### 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.

### How to solve a system of linear equations graphically (example)

VIDEO
2:22 minutes

Sal graphs the following system of equations and solves it by looking for the intersection point: y=7/5x-5 and y=3/5x-1.

### Solve systems of equations graphically

PRACTICE PROBLEMS

Graph a system of equations in slope-intercept or standard form, and find their solution using the graphs.

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

VIDEO
9:00 minutes

Sal uses 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

Sal solves another system of equations using elimination.

### How to solve a system of linear equations with elimination (basic example)

VIDEO
4:18 minutes

Sal solves the following system of equations by eliminating x: x-4y=-18 and -x+3y=11.

### Solve systems of linear equations with elimination (basic)

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

### Solve systems of linear equations with elimination (advanced)

PRACTICE PROBLEMS

Solve systems of equation with multi-step elimination (e.g., a manipulation is need in order for x-values or y-values to cancel each other out).

### Talking bird solves systems of equations with substitution

VIDEO
5:21 minutes

Sal solves a systems of equations with substitution.

### How to solve a system of linear equations with substitution (example)

VIDEO
4:21 minutes

Sal solves the following system of linear equations using substitution: -3x-4y=-2 and y=2x-5.

### Solve systems of linear equations with substitution

PRACTICE PROBLEMS

Solve systems of equations where one of the equations is solved for one of the variables.

### Solve any system of two linear equations

PRACTICE PROBLEMS

Solve systems of equations with any number of solutions using any solution method.