X*y=72
x = 5y-2
x=72/y
72/y=5y-2
72=5y^2-2y
5y^2 -2y - 72 = 0
(5y+18)(y-4)=0
y = -18/5 discard
or y = 4
4x=72
x=18
(18,4)
You need to find out 0,5$ is what pourcentage of 2$
So you need to do a cross product :
0,5 → 2
× → 100
(0,5 × 100) ÷ 2 → 50 ÷ 2 = 25%
So the answer is : The percent markup that is being charged is 25%!
Another way to see it is :
There is 4 times 0,5$ in 2$
So if you take 1/4 of 2$ it’s the same thing as saying that you’re taking 0,5$.
And 1/4 = 25% :)!