Can someone check this for me? its easy

this is the assignment:
in your journal, give an example of a function. give the relation as a set of ordered pairs. use a test such as mapping or the vertical line test to show if your set of ordered pairs is a function. an example of a function could be: distance traveled and time, or the cost of a turkey and its weight. you can list your relation as a set of ordered pairs, or as a table. in either case, you must prove the relation is a function using one of the two tools given to you in the prior lessons.

this is what i put:
the function is the cost of a car vs. the amount of time it takes in hours.
the parts for the repair cost $150 than an ordered pair would be (0, 150). if the labor rate is $50/hr., then another order pair would be (1, 150), (2, 200), (3, 250) etc. every time, you increase the x-coordinate by 1, you increase the y-coordinate by 50. the relation would be a function because there will not be two different costs that take the same amount of time.

step-by-step explanation:

30% of $420 is 0.30($420) = $126 and $420 + $126 = $546.

or, 130% of $420 is 1.3($420) = $546.

notice that this is not the $600 original list price with which we started.

why doesn't this work?

the method does not work because 30% of $420 is not the same amount as the 30% of $600. it may seem obvious when stated this way, but it is a very common error made on problems of this type. we cannot just use the same percent and get back to the original amount because we are taking that percent of a different value.

to work problems of this type correctly, it is generally best to write an equation for the situation and then solve.

example: since (100% – 30%)(original price) = (sale price)

70% of the   (original price) is $420.

0.7x   = 420

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x = 600

the original cost was $600.

we may also solve this problem using the two-step method. working the problem in two steps requires us to use more algebra skills. we have to know that x = 1x (identity property of multiplicationtext annotation indicator) and that 1x – 0.3x = 0.7x (subtracting like terms). then we solve the problem as follows:

(original price) – 30%(original price) = sale price

x – 0.3x = 420

0.7x = $420

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x = 600

the original cost was $600.  

note that with both of the above methods we do obtain the correct original amount.

example: after a 5% pay raise, hermione is earning $22,680 per year. what was she earning before the pay raise?

105% of (original salary) = current salary

1.05x = 22,680

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x = 21,600

hermione earned $21,600 per year before the pay raise.

this is an example so maybe you will get how to at least do it!

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step-by-step explanation:

8+8+6+6