Answer:
-68/7
Step-by-step explanation:
slope1 of Car 1 that pass (-5,-8) (2,7)
= (y1-y2)/(x1-x2)=(2-(-5))/(7-(-8))=7/15
Slope2 of car 2 that pass (5,1) (10,y)
slope 1 and slope2 are perpendicular =>slope 2 =-15/7
make slope2 y=(-15/7)x+b
for it pass(5,1) => 1=(-15/7)5+b =>b=82/7 => y=(-15/7)x+82/7
put (10,y) in => y=(-15/7) 10+82/7=-68/7
