We are given with the formula
p = 200k - 500
a) The constraint for this formula is obtained from the idea that the profit must be positive
200k - 500 > 0
k > 500/200
k > 2.5
b) To make 14000 profit
14000 = 200k - 500
k = 72.5 or 73 knives must be sold
The work is shown in the attached images. Each equation is labeled for slope intercept and standard form
y=-1/5x +18/5
5y+x=18
Add 5.2 and -8 = -2.8
And add 3.6x and x =4.6x
Your answer: 4.6x-2.8