It’s a function because the number doesn’t repeat
The correct answer is C.
Perpendicular lines have opposite reciprocal slopes. This mean you will flip the original number upside down, and change its sign (negative to positive and vice versa). So, the opposite of -1/4 will be 4.
recall d = rt, distance = rate * time.
let's say airplane A is going at a rate of "r", therefore airplane B is moving faster, at a rate of "r + 80".
now, after 3 hours, both planes have been travelling for 3 hours each, and say if A has covered "d" miles, then B has covered the slack of 2490 - d.
![\bf \leftarrow \underset{A}{\stackrel{r}{\rule[0.22em]{8em}{0.25pt}}}dallas\underset{B}{\stackrel{r+80}{\rule[0.22em]{18em}{0.25pt}}}\to \\\\[-0.35em] ~\dotfill\\\\ \begin{array}{lcccl} &\stackrel{miles}{distance}&\stackrel{mph}{rate}&\stackrel{hours}{time}\\ \cline{2-4}&\\ plane~A&d&r&3\\ plane~B&2490-d&r+80&3 \end{array}](https://tex.z-dn.net/?f=%5Cbf%20%5Cleftarrow%20%5Cunderset%7BA%7D%7B%5Cstackrel%7Br%7D%7B%5Crule%5B0.22em%5D%7B8em%7D%7B0.25pt%7D%7D%7Ddallas%5Cunderset%7BB%7D%7B%5Cstackrel%7Br%2B80%7D%7B%5Crule%5B0.22em%5D%7B18em%7D%7B0.25pt%7D%7D%7D%5Cto%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill%5C%5C%5C%5C%20%5Cbegin%7Barray%7D%7Blcccl%7D%20%26%5Cstackrel%7Bmiles%7D%7Bdistance%7D%26%5Cstackrel%7Bmph%7D%7Brate%7D%26%5Cstackrel%7Bhours%7D%7Btime%7D%5C%5C%20%5Ccline%7B2-4%7D%26%5C%5C%20plane~A%26d%26r%263%5C%5C%20plane~B%262490-d%26r%2B80%263%20%5Cend%7Barray%7D)
