### Home > AC > Chapter 9 > Lesson 9.1.1 > Problem 9-7

Solve the problem below by writing and solving an equation. A Guess and Check table may help you write the equation. Be sure to define your variable.

There are a total of

Let *n* = the number of countries in North America.

2 *n* = number of countries in Europe

2 *n* + 7 = the number of countries in Africa

The total number of countries in all three continents is 122.

*n* + (2*n*) + (2*n* + 7) = 122

*n* = 23

So, there are 23 countries in North America.

Remember to find the number of countries in Europe and Africa.