The map of a biking trail is drawn on a coordinate grid. The trail starts at P(−2, 1) and goes to Q(6, 1). It goes from Q to R(6, −3) and then to S(9, −3). What is the total length (in units) of the biking trail? A)11 B)15 C)18 D)19

Plug the points into the distance formula.

d= (sqrt) (x2-x1)^2+(y2-y1)^2

Plug the first set of points in. (-2,1) (6,1)

d= (sqrt) (6-(-2))^2+(1-1)^2
d= (sqrt) (6+2)^2+(0)^2
d= (sqrt) 8^2+0
d= (sqrt) 64
d= 8

Now, find the distance for the other two points. (6,1) (6,-3)
Q to R.
d= (sqrt) (x2-x1)^2+(y2-y1)^2
d= (sqrt) (6-6)^2 +(-3-1)^2
d= (sqrt) 0^2+-4^2
d= (sqrt) 16
d= 4

Now, finally, find the distance between R and S. (6,-3) and (9,-3)

d= (sqrt) (x2-x1)^2 + (y2-y1)^2
d= (sqrt) (9-6)^2+ (-3-(-3)^2
d= (sqrt) 3^2+ 0^2
d= (sqrt) 9
d= 3

Now, add all those distances together.

8+4+3= 15

"B" is the correct answer. 15 units.

I hope this helps!
~kaikers