Question 914334
Let p be constant of proportionality (meaning in this case, price)
let c be cost of a trip
let d be distance of a trip


The direct variation description gives {{{c=pd}}}, for c varies directly with d.


Now, your values given are supposed to mean, {{{84=p*140}}}, which allows you to find p.
{{{p=84/140}}}
{{{highlight_green(p=0.6)}}}, Php per kilometer


The more specific equation is now {{{c=(0.60)d}}}.
If d=320, then {{{highlight(c=(0.60)(320)=highlight(192))}}}  Php.


Problem question written more clearly than your other posting.