The biking miles range from 10 to 13 approximately and the smallest division is 1/2 mile, so a line plot consists of a range of 6 1/2 miles. These subdivisions can be marked out on the line: 10 1/2 (10.5), 11 1/2 (11.5), 12 and 12 1/2 (12.5). The frequency is the number of days of the week the biking distances were travelled, so there are two crosses stacked over 10.5, one over 11.5 and 12, and 3 over 12.5. That makes 7 crosses altogether for the week.
Count the total number of crosses over the marks from 10 to 12, that is, 10.5, 11.5 and 12. The total is 4. Since there are 7 crosses altogether, the fraction between 10 and 12 is 4/7.
The difference between the least and most miles biked is 12.5-10.5=2, the rightmost mark take away the leftmost.
The total number of miles biked is 2*10.5+11.5+12+3*12.5=21+23.5+37.5=21+61=82 miles.