Right away we know we don't have fractions; the midpoint is the average of the coordinates, so if it and one endpoint are integers so is the other endpoint.
We can do a kind of point arithmetic:
C = (A+B)/2
2C = A+B
B = 2C - A
B = 2(6,1) - (1,3) = (12,2)-(1,3)=(11,-1)
Answer: That's none of the above, but a typo away from the first choice.
Answer:
Equation to represent the situation = 
Step-by-step explanation:
Given:
Initial investment = Y
Growth rate (r) = 5% = 5 / 100 = 0.05
Number of year (n) = X year
Amount after X year = $800
Find:
Equation to represent the situation:
Computation:

Equation to represent the situation = 
Decimal is 0.12 and fraction is 12/100
Because we know the midpoint is in the middle, we know that both sides are equal.
So set both = to each other
4x - 1 = 3x + 3
add 1 to both sides
4x=3x+4
then subtract 3x from both sides and because there is always a 1 in front of x the answer would be
x=4