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3 years ago

The sum of twice a number and seven is 13. Find the number.

Mathematics

1 answer:

Furkat [3]3 years ago

3 0

Answer:

<h2>The answer is 3</h2>

Step-by-step explanation:

Let the number be x

The statement

twice a number is written as

The sum of twice a number and seven is written as

2x + 7

The result is 13

So we have

2x + 7 = 13

Subtract 7 from both sides

That's

2x + 7 - 7 = 13 - 7

2x = 6

Divide both sides by 2

That's

$\frac{2x}{2} = \frac{6}{2}$

We have the final answer as

Hope this helps you

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The chemistry class was making 300 gallons of 30% isopropyl alcohol. They mixed 12% with 42%. How much of each did they use?

alexgriva [62]

Answer:

<u>The chemistry class mixed 120 gallons of 12% isopropyl alcohol and 180 gallons of 42% isopropyl alcohol.</u>

Step-by-step explanation:

1. Let's review the information given to us to answer the question correctly:

Amount of isopropyl alcohol made by the chemistry class = 300 of 30%

Amount of 12% isopropyl alcohol mixed by the chemistry class = x

Amount of 42% isopropyl alcohol mixed by the chemistry class = 300 - x

2. How much of each did they use?

Let's write our equation to solve for x, this way:

30% = 0.3, 12% = 0.12, 42% = 0.42

0.12x + 0.42 (300 - x) = 0.3 * 300

0.12x + 126 - 0.42x = 90

-0.3x = 90 - 126

-0.3x = -36

x = -36/-0.3

<u>Let's prove x = 120 is correct</u>

0.12x + 0.42 (300 - x) = 0.3 * 300

0.12 * 120 + 0.42 (300 - 120) = 0.3 * 300

14.4 + 75.6 = 90

90 = 90

<u>We proved x = 120 is correct</u>

5 0

3 years ago

Solve the equation for all values of x.<br> (8x+9)(49x^2-100)=0

Liono4ka [1.6K]

Answer:

$x = \frac{-9}{8} , \frac{-10}{7} , \frac{10}{7}$

Step-by-step explanation:

8x+9=0

8x=-9

$x = \frac{-9}{8}$

$49x^{2}-100 = 0$

$(7x)^{2} -10^{2} =0$ ,

$(7x+10)(7x-10)=0$

$7x+10=0, 7x-10=0$

$7x=-10, 7x=10$

$x=-\frac{-10}{7}$ , $x = \frac{10}{7}$

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2 years ago

Please help I am struggling please

Katen [24]

Answer:

x = 8sqrt3

y=8

Step-by-step explanation:

cos60=y/16

y=16cos60

y=16x1/2

y=8

sin60=x/16

x=16sin60

x=(16sqrt3)/2

x=8sqrt3

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2 years ago