x-1.19/x=0.30 solve for x

Question

I'm trying to determine how to solve for what SRP would give me a 30% profit with a cost of $1.19.

Answer 1

x - (1.19/x) = 0.30

multiply both sides by x

x^2 - 1.19 = 0.30x

subtract 0.30x from both sides

x^2 - 0.30x - 1.19 = 0

quadratic formula

x = (0.3 +- sqrt (0.3^2 - 4(1)(-1.19) ) ) /2(1)

x = (0.3 +- sqrt(0.09 + 4.76) )/2

x = (0.3 +- sqrt(4.85) )/2

x = (0.3 +- 2.20)/2

it's money and we can't have negative money, so:

x = (0.3 + 2.2)/2

x = 2.5/2

x = 1.25