the distance between Lutherville and Otisburg is 240 - 150 = 90.
Planet Diner is half-way between them, half of 90 is 45.
Planet Diner is 45 miles from Lutherville.
from Clark to Lutherville is 150 miles, and from Lutherville to Planet Diner is 45 miles, thus from Clark to Planet Diner is 150 + 45 = 195.