The answer is 83. First divide 10 by 2, which is 5 for a remaining 85-5+3. 85 - 5 is 80 and 80 + 3 is 83.
That's a quadratic, a nice parabola in vertex form.
The parabola has a positive x^2 term, so it's a CUP, concave up positive. It will have a minimum at the vertex, which is (2,5). Plot that point.
Now we need a couple of guide points to draw the usual parabola going up from both sides of its vertex. We try x=0 giving (0,9) and see that x=4 also gives 9, (4,9). Plot the parabola through those two points and the vertex and you're done.
The answer to number seven is EDF!
Hence, there is 5 gallons of fuel Roselyn needed for her journey.
