Given:

In the given figure, PS=x, RS=35, UV=20, VW=25 and TW=15
To find:
The scale factor from PQRS to TUVW.
Solution:
We have,

We know that the corresponding sides of similar figures are proportional. The scale factor is the ratio of one side of image and corresponding side of preimage.
The scale factor is:



Therefore, the scale factor from PQRS to TUVW is
.
Answer: A; 6.3%
Step-by-step explanation:
Problem 1
For the first problem, we first want to find y so that we can plug it into the expression.
We can use elimination method for the system of equations to solve.
3x+3y=21
3x-y=5
We subtract both equations to eliminate x.
4y=16 [divide both sides by 4]
y=4
Now that we know y, we can plug it into the expression.
[divide]
[subtract]

We know that the answer is A.
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Problem 2
For the second problem, we need to know how to calculate percent error. The formula for precent error is
. We know that the exact value is 80 because the buyer was supposed to given 80. 75 is the measured value because that was what the buyer was given.
[subtract]
[solve absolue value]
[divide]
[multiply]

Since the problem said to round to one decimal place, we know that the answer is 6.3%.
What is the rest of the problem? I can help you!
When rounding the 4 you look to the right of the number, which is the 4, and if the number is higher than 5 you would change the 4 to 5.
Therefore: 71.5