Srry i do not see the dot plot.
When the ball hits the ground, the height is 0.
0 = 100 - 16t²
0 = (10 - 4t)(10 + 4t)
0 = 10 - 4t or 0 = 10 + 4t
4t = 10 or -4t = 10
t =
or t = 
Time cannot be negative (unless you have a time machine) so disregard 
Answer: t =
= 2.5 seconds
16.7 is the answer rounded to the nearest tenth.
You can find the remainder right away by simply plugging in

. The polynomial remainder theorem guarantees that the value of

is the remainder upon dividing

by

, but I digress...
Synthetic division yields
3 | 2 -11 18 -15
. | 6 -15 9
- - - - - - - - - - - - - - - - -
. | 2 -5 3 -6
which translates to

(and note that

, as expected)
N = 273
273 / 7 = 39
Dividend / divisor = quotient
Work Backwards:
n/7 = 39
n = 39 X 7
n = 273