Which ordered pair is the solution to the system of linear equations y = negative 7 x + 2 and y = 9 x minus 14?

(1, -5) is the solution of the system

Step-by-step explanation:

y = negative 7 x + 2 should be written as  y = -7x + 2, and

y = 9 x minus 14 as y = 9x - 14

Use elimination by substitution to solve this system.  Equate the two equations together to eliminate y:  y = 9x - 14 = -7x + 2.

Combining like terms, we get 9x - 14 = -7x + 2  =>  16x = 16

Dividing both sides by 16 yields x = 1.

Substituting 1 for x in the first equation yields the corresponding y-value:

y = -7(1) + 2 = -5

Thus, the ordered pair (1, -5) is the solution of the system.

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

equation image indicator

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

equation image indicator

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

equation image indicator

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!

9x