Check the picture below.
thus is at 0 = -16t² + 96t +640,

well, clearly it can't be a negative value for the elapsed seconds, so it can't be -4.
The distance between Branch A and Branch B is given by the Pythagoras theorem
AB² = (Vertical Distance)² + (Horizontal Distance)²
AB² = (4-1)² + (1 - -3)²
AB² = 3² + 4²
AB² = 9 + 16
AB² = 25
AB = 5
BC² = (Vertical distance)² + (Horizontal distance)²
BC² = (-2 - 4)² + (5-1)²
BC² = (-6)² + (4)²
BC² = 36 + 16
BC² = 52
BC = 7.21
Half way of BC = 7.21 ÷ 2 = 3.6 miles
Total distance travelled from A to B and then halfway from B to C is 3.6+5 = 8.6 miles
18 with a remainder of 26 I got this by using a long division calculator I hope this helps you
I think the answer is x=2 <span />