The distance is 18 units and the equation would be (-8 - 10)
You can just do rise over run to find the slope or use the slope equation which is

3=x1
0=x2
5=y1
-1=y2
input those and you can get the slope graphed.
Based on the model, 28.6 is the estimated increase, in inches, of a boy’s height each year.
I'll use my own formula (similar to yours tho)

A=future amount
p=invested
r=rate in decimal
n=number of times per year compounded
t=time in years
so
when will A=2P
subsitute 2P for A
also quarterly means 4 times a year or n=4
and 12%=0.12=r
so

divide both sides by P

simplify


take the ln of both sides



divide both sides by 4ln(1.03)

use calculator
5.86244=t
about 5.9 years