"Starting with three, every consecutive line has 2 less than twice the previous line."
this statement means that
your staring line has 3 marbles. You multiply the 3 marblesby 2 so
3x2=6
And then you minus it by 2
6-2=4
which means that you'll get 4 marbles for the next line.
So to get your 6th line, you count how many marbles is on the 5th line but since your diagram doesn't have the 5th line you have to figure out the 5th line by counting how.many marbles is on the 4th line.
4th line = 10 marbles
10×2=20
20-2=18
5th line = 18
18×2=36
36-2=34
So the 6th line has 34 marbles.
The answer to that is 80 percent as a fraction is 8/10
Substitute this into the parabolic equation,
We're told the line 
intersects 
twice, which means the quadratic above has two distinct real solutions. Its discriminant must then be positive, so we know
We can tell from the quadratic equation that has its vertex at the point (3, 6). Also, note that
and
so the furthest to the right that extends is the point (5, 2). The line passes through this point for 
. For any value of 
, the line passes through either only once, or not at all.
So 
; in set notation,
Cannot reduce, it is already in simplest form. You can convert it to a decimal though, 0.671875
