The applicable formula is
A = P(r/12)/(1 -(1+r/12)^(-12n))
where P is the principal amount,
r is the annual interest rate (compounded monthly), and
n is the number of years.
Using the formula, we find
A = 84,400*(0.04884/12)/(1 -(1+0.04884/12)^(-12*15))
= 84,400*0.00407/(1 -1.00407^-180)
= 343.508/0.518627
≈ 662.34
The monthly payment on a mortgage of $84,400 for 15 years at 4.884% will be
$662.34
The first two are equivalent to 15 = k + 13
8 = k + 13 - 7 → ( add 7 to both sides )
8 + 7 = k + 13 ⇒ 15 = k + 13 ' is equivalent '
12 = k + 13 - 3 → ( add 3 to both sides )
12 + 3 = k + 13 ' is equivalent '
Another way to solve this is to use the Midpoint Formula. The midpoint of a segment joining points

and

is

So the midpoint of your segment is

Perhaps it helps to see that the x-coordinate of the midpoint is just the average of the x-coordinates of the points. Ditto for the y-coordinate of the midpoint; just average the y's.
So it cooks for 2 hrs and 20 minutes......and it has to be done by 1 pm.
so from 1 p.m. - 2 hrs = 11 a.m........- 20 minutes = 10:40 a.m
start cooking at 10:40 a.m. and it will be done by 1 p.m