Honestly I believe the snail would travel 2.5 more centimeters in 6 minutes. so technically the snail traveled 12.5 cm in 6 minutes.
8 units
(This is how I get the answer)
We know that the initial temperature is -3 then it rises to 8 and drops by 6 degrees then you just need to subtract six from 8 
Use the (-b + - sqrt( b^2 - 4ac) ) /2a Formula.
a = 1 b= 10 c= 24
so you get .. (x+6 )(x+4) A