A runner competes in a local marathon. He places 34th which is exactly the top 40% of all runners. How many runners competed

85 runners

Step-by-step explanation:

we know that

34th represent 40% of all runners

so

using proportion

Find out the total number of runners

5x+40

5(x + 8)

7x - 49

7(x - 7)

18x + 9

9(2x + 1)

15x - 10

5(3x - 2)

step-by-step explanation:

for number one all you have to do is factor 5 out of 5x + 40

for number 2 factor 7 out of 7x - 49

for number three factor 9 out of 18x + 9

for number four factor 5 out of 15x - 10

b. 153 students do not participate in sports and seventy-five 12th graders were surveyed