Help me solve x² - 5x - 4?

Question

In this question, they say 30 - x = 17 and x + y = 23. So, therefore, we can say that x = 13 and y = 10. From that, when I solve it, the above equation x² - 5x - 4 = 169 - 165 - 4 = 0 But the answer says that it's x² - 5x - 4 = 169 - 165 - 4 = 100... which means your answer is the choice y². How is that even possible?!

Answer 1

It's because you got the wrong answer for 5x.

Let x = 13.

5x = ?

5(13) = 65.

It is not 165, but 65.

Therefore, 169 - 65 - 4 = 100.