Answer:
9 essay questions.
Explanation:
Let x be the number of multiple choice questions and y be the number of essay questions.
We have been given that Diego’s history teacher writes a test for the class with 26 questions. We can represent this information in an equation as:
![x+y=26...(1)](https://img.qammunity.org/2020/formulas/mathematics/high-school/49aujhqaebizqmrh53y9leqgn41if2zgb2.png)
We are also told that multiple choice worth 3 points each, so total number of points for x questions will be 3x.
As essays worth 8 points each, so total number of points for y questions will be 8y.
Since the test is worth 123 points, so we can represent this information in an equation as:
![3x+8y=123...(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/ukhjr4c8pqoo2m2un9rsa8eso3t6saxx8a.png)
Now we will use substitution method to solve system of linear equations.
From equation (1) we will get,
![x=26-y](https://img.qammunity.org/2020/formulas/mathematics/high-school/zp34vxi4njwynt2anva6pxdf7l40ljadof.png)
Substituting this value in equation (2) we will get,
![3*(26-y)+8y=123](https://img.qammunity.org/2020/formulas/mathematics/high-school/pzey9m8fcwj7z27g27oaz75sxkb6a77isa.png)
![78-3y+8y=123](https://img.qammunity.org/2020/formulas/mathematics/high-school/7wqdiiszjsk2avsu8szcv1nocnn4c888bi.png)
![78+5y=123](https://img.qammunity.org/2020/formulas/mathematics/high-school/pwaq64x4114srj3joi7i7edlxiy4wropha.png)
Let us subtract 78 from both sides of our equation.
![78-78+5y=123-78](https://img.qammunity.org/2020/formulas/mathematics/high-school/u2te09rjo83erpysdcsoc6zuz8rpzh4638.png)
![5y=45](https://img.qammunity.org/2020/formulas/mathematics/high-school/jacyhaamtcqnhsdicuj7riexmlu1alevle.png)
Let us divide both sides of our equation by 5.
![(5y)/(5)=(45)/(5)](https://img.qammunity.org/2020/formulas/mathematics/high-school/gn317u528wmmov1fl4jza19qlnj9vmpo3d.png)
![y=9](https://img.qammunity.org/2020/formulas/mathematics/high-school/lbe7cetkyupszfsu17lale83fwrr9twib5.png)
Therefore, there were 9 essay questions in the test.