General Idea:
(i) Assign variable for the unknown that we need to find
(ii) Sketch a diagram to help us visualize the problem
(iii) Write the mathematical equation representing the description given.
(iv) Solve the equation by substitution method. Solving means finding the values of the variables which will make both the equation TRUE
Applying the concept:
Given: x represents the length of the pen and y represents the area of the doghouse
<u>Statement 1: </u>"The pen is 3 feet wider than it is long"

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<u>Statement 2: "He also built a doghouse to put in the pen which has a perimeter that is equal to the area of its base"</u>

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<u>Statement 3: "After putting the doghouse in the pen, he calculates that the dog will have 178 square feet of space to run around inside the pen."</u>

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<u>Statement 4: "The perimeter of the pen is 3 times greater than the perimeter of the doghouse."</u>

Conclusion:
The systems of equations that can be used to determine the length and width of the pen and the area of the doghouse is given in Option B.

Answer:
she spent 75%
Step-by-step explanation:
Alrighty!
*Note the ">" sign is similar to the "=" sign.
3m - 3(3m + 8) > 3m
3m - 6m + 24 > 3m (distribute)
-3m + 24 > 3m (combine like terms)
24 > 6m (Compute/simplify)
8 > m
Makes sense?
(1,5)
To find this, do the opposite of how you got to (4,5).
Move right 2 units instead of left.
Move left 5 units instead of right.
Now, your on the point (1,5).
To check this, do what they said. (Move left 2 units and right 5 units) If its correct you end up on (4,5)
Answer:
8978 grams
Step-by-step explanation:
The equation to find the half-life is:

N(t) = amount after the time <em>t</em>
= initial amount of substance
t = time
It is known that after a half-life there will be twice less of a substance than what it intially was. So, we can get a simplified equation that looks like this, in terms of half-lives.
or more simply 
= time of the half-life
We know that
= 35,912, t = 14,680, and
=7,340
Plug these into the equation:

Using a calculator we get:
N(t) = 8978
Therefore, after 14,680 years 8,978 grams of thorium will be left.
Hope this helps!! Ask questions if you need!!