Answer :
You want to find the time (x) when the distance from desitnation is 0:
d = 0,
d(x) = 1375 - 110x
0 = 1375 - 110x
110x = 1375
x = 1375/110
x = 12.5 hrs
d = 0,
d(x) = 1375 - 110x
0 = 1375 - 110x
110x = 1375
x = 1375/110
x = 12.5 hrs