Basic Math - Subtraction with Whole Numbers

A city bus has five stops left on its route. At the first stop, people get off. At the second stop, get off. At the third, no one gets off. At the fourth, people get off. At the fifth, there are people left on the bus, and they all get off. How many people were on the bus before the first stop?

Explanation

To solve, create a linear equation:

represents the total number of people on the bus before the first stop.

We then subtract the amount of people that got off at each stop and set that equal to the number of people to get off at the final stop.

What is the solution of the above equation?

Explanation

We can show this using objects:

We can see that only 7 objects are left.

Paul had video games. On Monday, he gave video games to his friend Chris. On Tuesday, he sold of his video games to the local video game shop. On Wednesday, Paul accidentally broke video games and threw them away. How many video games does Paul have left?

Explanation

This is a simple subtraction problem.

First, subtract the number of video games Paul gave to Chris on Monday.

Now, subtract the number of video games Paul sold from the number he has left.

Finally, subtract the number of video games Paul broke and threw away.

What is the solution of the above equation?

Explanation

We can see that by the objects.

We can see that there is only one object left.

Solve for :

Explanation

To solve for n we need to isolate n on one side of the equation and all of the constants on the other side.

We do this by adding 15 to both sides.

Then we add 12 to both sides to get our final answer.

Timmy has sea monkeys. At the end of the first month that he has them, sea monkeys die, and his parents buy him new ones. At the end of the second month, more sea monkeys die. How many sea monkeys does Timmy have at the end of the second month?