Let's name the number 'n'. Now write an equation. 7*n +n^2 =12Now you can form a quadratic. n^2 +7n-12=0. Now you can use a myriad of methods to solve it. If you still need help, just message me.

which means

has no solution, and we can omit that factor.
This leaves us with

which occurs for

.
41% of students ran in 12 minutes or less.
Using the histogram we see that there were 2+12+11+9=34 students that ran. Out of those, 2+12=14 ran in 12 minutes or less (the first two bars).
14/34 = 0.411 = 41%.
6 halves is 3.
B is at 3 1/2
3 1/2 minus 3 is 1/2
D would be plotted at 1/2.