For this case we have to:
n: Represents the weight of Mary in Kg.
If your sister weighs 15 kg less we have:

Where "y" represents the weight of his sister in kg.
To find how many times Mary is heavier than her sister, we must divide Mary's weight by her sister's weight.
We have then:

Answer:
Mary is
times heavier than her sister.
Answer:
A. width = x - 4.5
B. 111 = 2(x + (x -4.5))
Step-by-step explanation:
A. The width is 4.5 meters shorter than x, so is x -4.5.
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B. The perimeter is twice the sum of length and width. It is 111 meters, so an equation for it could be ...
111 = 2(x + (x -4.5))
When talking about surveys (and most other things) we use 100% as the cap. You can not work harder than 100% efficiency and you can not have more than 100% of people agree with you. You can think of this as a pie.
A whole pie would be 100%
A half a pie 50%
Etc.
You can not have more than a whole pie (without adding another pie or variable in this case)
So when you look at this problem with that analogy in mind, all it is is simple addition and subtraction.
If you create a survey and 82% of people vote yes, how many, out of 100%, voted yes.
To find this we take 100% (The whole pie or everybody who voted) and - the portion of the pie we ate or everyone who voted yes, 82%, which will give us the answer, everyone who voted no or the pie that is left on the platter.
So your equation would be 100 - 82 =18
18% of people interview used internet someplace other than in the home. <span />
He worked 36 hours (9.57), and anything over that was over pay (14.36)
36 * 9.57 = 344.52
So, working his normal hours he got $344.52.
416.32 - 344.52 = 71.80
71.80/14.36 = 5
Therefore, he worked 5 hours of overtime.
R/ r+ 15 = 3/8
Cross multiply: top of one side multiplied by bottom of other side:
R x 8 = 3 x r+ 15
Simplify:
8r = 3r + 45
Subtract 3r from both sides:
5r = 45
Divide both sides by 5:
R = 9