The answer should be 103. Because the interior angles of all triangles add up to 180 degrees, you can just add together the two known interior angles; subtract them from 180; and then find the supplement.
Answer:
For 600600 miles, it will use
(600600*55)/120120 = 275 gallons
Using 3030 gallons, it can travel
(3030*120120)/55 = 6617520 miles
1\3h-2.7+12=2\3h-6
-2.7+12+6=2\3h-1\3h
15.3=1\3h multiply both sides by 3
45.9=h