If the line through A(1, −1) and N(4, t) has slope 5, what is t?

Correct answer: b 14

(t + 1)/(4 − 1) = 5, so t + 1 = 15 and t = 14.

Why the other options are wrong

• a 15: 15 is t + 1; so t = 15 − 1 = 14. (t + 1)/(4 − 1) = 5, so t + 1 = 15 and t = 14.
• c 8/5: (t + 1)/(4 − 1) = 5, so t + 1 = 15 and t = 14. So 8/5 is not the answer.
• d −2/5: (t + 1)/(4 − 1) = 5, so t + 1 = 15 and t = 14. So −2/5 is not the answer.