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, 
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