X represents hours , which means 62 miles per hours equals 62x. Since Ed has already traveled 239 miles the opposite would be to add in order to subtract in the equation. 672 would be the equivalent of traveling 672 miles in x hours.
Two significant Figures I believe because you want to go with the least amount of sig figs that are already in your problem which would be 2 in 7500 because the zeros are not significant
It has to be wider than the first two arcs or else you will just get two circles side by side with point c in common. I usually measure it to be the length of a point between the c and j. It is a good point to get the arcs to intersect.
