After 3 hours, you will be on 450 mile marker.
Step-by-step explanation:
<u>step 1:</u> At start, the number in the mile marker is 100
<u>step 2:</u> After 4 hours, the number in the mile marker is 300
<u>step 3:</u> The difference of 300-100= 200. In 4 hours you crossed 200 mile markers.
<u>step 4:</u> Therefore, for 1 hour you can cross= 200/4= 50 mile markers.
For 3 hours, the number of mile markers crossed= 3*50= 150 mile markers.
<u>step 5:</u> After 3 hours, the number in the mile marker will be= 300+150= 450