So check the picture below
if we check the solutions or zeros for the equation, we get

and as you can see in the picture, the value of "x" when y = 3.5, or the height of the truck is

the truck, ends up with a clearance of

on either side, so, the maximum clearance, the truck can have, those two clearances added together,
He will need 6 tenth size strips because if you put 3/5 vertically with another fraction beside of it that had the numerator blank and the bottom 10. You do this because Jeff uses fifth size strips so 5 represents the strips and you need tenth size strips so you find our numerator for the tenth size strips. You find out how many times 5 can go into 10 or 5 times what equals 10 and it's 2. So whatever you do to the bottom you do to the top. You times 5 by 2 at the bottom and get 10 for the tenth size strips and 3 times 2 at the top yoi get 6 and that is 6/10 is your answer