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3 years ago

4x−2y=14 y=12x−1 solve by substitution

Mathematics

1 answer:

Tatiana [17]3 years ago

8 0

Answer:

x= -3/5

Step-by-step explanation:

4x-2y=14

y=12x-1

4x-2(12x-1)=14

4x-24x+2=14

4x-24x=12

-20x=12

×= -12/20

x= -3/5

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What property is 1/5+1/8=1/8+1/5?

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3 years ago

The average heights of x number of girls and 15 boys is 123. if the average heights of boys is 125 and that of girls is 120.find

mamaluj [8]

Answer:

$x = 10$ . In other words, there number of girls is $10$ .

Step-by-step explanation:

The average of a number of measurements is equal to the sum of these measurements over the number of measurements.

$\displaystyle \text{Average} = \frac{\text{Sum of measurements}}{\text{Number of measurements}}$ .

Rewrite to obtain:

$\begin{aligned}& \text{Sum of measurements}= (\text{Number of measurements}) \times (\text{Average}) \end{aligned}$ .

For this question:

$\begin{aligned}& \text{Sum of heights of boys} \\ &= (\text{Number of boys}) \times (\text{Average height of boys}) \\ &= 15 \times 125 = 1875\end{aligned}$ .

$\begin{aligned}& \text{Sum of heights of girls} \\ &= (\text{Number of girls}) \times (\text{Average height of girls}) \\ &= x \times 120 = 120\, x\end{aligned}$ .

Therefore:

$\begin{aligned}& \text{Sum of boys and girls} \\ &= \text{Sum of heights of boys} + \text{Sum of heights of girls}\\ &= 1875 + 120\, x\end{aligned}$ .

On the other hand, there are $(15 + x)$ boys and girls in total. Using the formula for average:

$\begin{aligned}& \text{Average height of boys and girls} \\ &= \frac{\text{Sum of heights of boys and girls}}{\text{Number of boys and girls}} \\ &= \frac{1875 + 120\, x}{15 + x}\end{aligned}$ .

From the question, this average should be equal to $123$ . In other words:

$\displaystyle \frac{1875 + 120\, x}{15 + x} = 123$ .

Solve this equation for $x$ to obtain:

$1875 + 120\, x= 123\, (15 + x)$ .

$(123 - 120)\, x = 1875 - 123 \times 15$ .

$x = 10$ .

In other words, the number of girls here is $10$ .

5 0

3 years ago

One angle of an isosceles triangle is 80º. What are the other two angles?

eimsori [14]

Answer:

80 and 20

Step-by-step explanation:

80+80+20=180

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3 years ago

Suppose you can work at most a total of 25 hours per week. Baby-sitting, x, pays $6 per hour and working at the grocery store, y

Andrei [34K]

Answer:

y=7 number of hours at grocery store

x=18 number of hours at baby- sitting

Step-by-step explanation:

According to the information provided.

x is number of hours at baby- sitting

y is number of hours at grocery store

total number of hours worked

1) x+y =25

total earn in a week

2) x*$6 + y* $9 = $171

from equation 1

x+y=25

x= 25-y

we place the above derived equation in equation 2

x*$6 + y* $9 = $171

(25-y)*$6 + y* $9 = $171

(25*6) -6y +9y =171

150+3y=171

3y=171-150

3y=21

y=7 number of hours at grocery store

x= 25-y

x= 25-7

x=18 number of hours at baby- sitting

3 0

3 years ago