Answer:
Let the first trip be x
Second trip is 2x-4
Third trip is 2(2x-4)
Fourth trip is 3x + 18
x + (2x-4) + 2(2x-4)+3x+18 = 426
x + 2x -4 + 4x - 8 + 3x + 18 = 426
10x + 6 = 426
10x = 426-6
x = 420/10 = 42 km
Second trip was
2x-4 = 2(42)-4 = 84-4 = 80 km
Third trip was
2 * 80 = 160 km
Fourth trip was
3(42) + 18 = 144 km