To work this out you would need to find the 25% decrease of 560. To do this you would first divide 25 by 100, which gives you 0.25. Then you would minus 0.25 from 1, which gives you 0.75. This is because when finding percentage decreases you would first have to convert it into a decimal. Then you would have to minus it from 1 , to make sure that it will be a 25% decrease not a 75% decrease. Then you would multiply 560 by 0.75, which gives you 420.
Well obviously the two bottom graphs don't represent the two trucks meeting. So we can cross those out. Looking at the top two graphs we can tell that the line above is truck #2. In graph 1 it shows the second truck is slowing down which is wrong since that isn't told.
It should be 7.97 decigrams, since you want to convert 3 milligrams to decigrams (0.03), it is asking "How much more" which means you subtract. 8 subtracted from 0.03 is 7.97.