20. Rafael has a business selling computers. He buys computers from the manufacturer for $450 each and sells them for $800. Each month, he must also pay fixed costs of $3000 for rent and
utilities at his store. If he sells n computers in a month, which of the following equations can be used
to calculate his profit?
A. P = n(800 - 450)
B. P = n(800 - 450 - 3000)
C. P = 3000n(800 - 450)
D. P = n(800 - 450) - 3000
E. P = n(800 - 450) + 3000
Yeah

D , p = n (800 - 450) - 3000

Step-by-step explanation: Firstly, you have to account for how much money Rafael is making off of each computer (800 - 450). That factor is then multiplied by the variable "n" which represents the amount of computers sold. Lastly, since this is an equation to calculate his monthly profits, you have to subtract the rent that he is paying ($3000) from the total profit that he made off of selling the computers. Therefore, giving you the equation

P (profit) = n (amount of computers sold) (800-450) - 3000 (rent).

option (b) is correct

step-by-step explanation:

to find the solution of this system, we need to convert it into reduced row-echelon form. we have,

after applying row operations r2 -> r2/2 and r3 -> r3/3, we get,