Answer: a is correct
Step-by-step explanation:
Let the actual value of the stool be x.
So if the carpenter sells the stool x rupees he neither loses, now wins anything.
67.50 is the value x - 10% of x, that is:
67.50=x-0.1x
67.50=0.9x
x=67.50/0.9=75 (rupees) is the actual value of the stool.
Selling the stool for 82.50 rupees, the carpenter clearly would make a profit, say of y% of that actual value, that is y%*75.
So using the same method:
82.50=75+y%*75
y%*75=82.50-75=7.5
we can make the calculations, but clearly 7.5 is 10% of 75
Answer: 10% gain.
https://www.wolframalpha.com/
14: 
56/8 = 7 so multiply 1/2 by 7/1 to get the unidentified fraction "x/y"
1/2 · 7/1 = 7/2 or 3 1/2
15. 
to get from 100 to 5, you would divide by 20, so to solve for x, multiply 2 by 20, to get a product of 40.
40/100 = 40% or D
16. 
A
<span>A common factor is a factor of 2 or more numbers.
the factors of 12 are: 1,2,3,4,6,12
the factors of 21 are: 1,3,7,21
1 and 3 are both common factors of 12 and 21.</span>
