C) (0.85 + x/100)(250+145) does not give the correct answer.
Explanation
A) works; adding the two costs together is 250+145=395. We multiply this by 0.85 because 100%-15%=85%=0.85. We also have x% tax, which is represented by x/100, added to 100% of the value, or 1.00. Altogether this gives us
395(0.85)(1+x/100) = 395(0.85 + (0.85x/100)) = 395(0.85) + 395(0.85x/100)
= 395(0.85) + 395(0.0085x)
B) works; we have 250+145 for the original price; we have 85% = 0.85 of the value; we also have 100% + x%, which is (100+x)/100.
C) does not work; (0.85+x/100)(395) does not take into consideration that you are finding the tax after taking the 85%. This will simplify out to
0.85*395 + (x/100)(395) = 335.75 + 395x/100 = 335.75 + 3.95x, which is too much.
D) works; simplifying the expression from A, we have 395(0.85) + 395(0.0085x) = 335.75 + 3.3575x.
All of the energy from the Sun that reaches the Earth arrives as solar radiation, part of a large collection of energy called the electromagnetic radiation spectrum. Solar radiation includes visible light, ultraviolet light, infrared, radio waves, X-rays, and gamma rays.
Let’s condense the original expression and see if that’s one of the answers
-1/2(-3/2 x + 6x + 1) - 3x
First we distribute the -1/2
((-1/2)(-3/2 x) + (-1/2)(6x) + (-1/2)(1)) -3x
3/4x - 3x - 1/2 -3x
Combine like terms
(3/4 x - 3x - 3x) -1/2
-21/4 x - 1/2
We could make this a mixed number
-5 1/4 x - 1/2
(Mixed number: 5 times 4 plus one gets the numerator)
So the answer is D
