Mathematics, 13.06.2020 05:57 21megoplin

Please help. 10 points and brainliest. Three times a number, x, plus four times a number, y, equals 81. Two times x minus four times y equals -46. Find the numbers by setting up a system of linear equations and solving the system using the elimination method.
x = 7, y = 15
x = 11, y = 9
x = 12, y= 11
x = -11, y = 13

Answers: 1

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Answer from: shawny5

x = 7, y = 15

Step-by-step explanation:

3x + 4y = 81

2x - 4y = -46 Add together both equations

5x = 35 Divide both sides by 5

x = 7

Plug this into the first equation

3x + 4y = 81

3(7) + 4y = 81 Multiply

21 + 4y = 81

-21 -21 Subtract 21 from both sides

4y = 60 Divide both sides by 4

y = 15

Answer from: u8p4

x = 7, y = 15

Step-by-step explanation:

First, set up the system of equations. You are given two statements which must be true in order to find the system.

First equation: Three times a number, x, plus four times a number, y, equals 81.

3x + 4y = 81

Second equation: Two times x minus four times y equals -46.

2x - 4y = -46

You can use the elimination method to solve for the variable x.

This method involves adding two equations together in order to remove one of the variables from the equation. The equations given are already prepared for the final step of elimination:

$3x + 4y = 81\\2x - 4y = -46\\\\(3x + 2x) + (4y - 4y) = (81 - 46)\\5x = 35\\x = 7\\\\$

The correct choice is the first choice given: x = 7, y = 15. No other answer choices given have x = 7.

Answer from: Quest

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Answer from: Quest

the speed is $135$ miles per hour > is false

step-by-step explanation:

we know that

a relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form $y/x=k$ or $y=kx$

in a proportional relationship the constant of proportionality k is equal to the slope m of the line and the line passes through the origin

the graph shown in the figure represent a direct variation

the slope of the line represent the speed

$y/x=k$

for the point $(1.5,90)$

substitute the values of x and y

$k=90/1.5=60\ miles/hour$

the linear equation is equal to

$y=60x$

statements

case a) it takes $2$ hours to go $120$ miles

the statement is true

because

substitute

for $x=2$

find the value of y in the linear equation

$y=60(2)=120\ miles$ > is correct

case b) the speed is $135$ miles per hour

the statement is false

because the speed is $60\ miles/hour$

case c) the unit rate for the trip is $60\ miles/hour$

the statement is true

because the speed is equal to the slope of the linear equation

case d) it took $20$ minutes to go the first $20$ miles

the statement is true

because

substitute

for $x=20\ minutes=(1/3)\ hour$

find the value of y in the linear equation

$y=60(1/3)=20\ miles$ > is correct

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Please help. 10 points and brainliest. Three times a number, x, plus four times a number, y, equals...