6. 6th grade- go to the two columns above $600, which is about 8 students in the first column and 5 students in the 2nd. 8 + 5 = 13, so 13 students in 6th grade earned $600 or more.
7th grade- again, go to the columns above $600, which is about 7 students in the first column and about 3 in the 2nd column. 7 + 3 = 10, so 10 students in 7th grade earned $600 or more.
Do the same thing for #7, just follow the rows exactly as #6.
Answer:
a straight line: y = x -5, with a hole at (4, -1)
Step-by-step explanation:
The rational function can be simplified to ...

The graph of this is a straight line, with a hole at x=4, where the function is not defined.
(60 minutes / 8 km)*(2 km) = 60/4 = 15 minutes