Explanation:
Pair 1 is true if Jeff's monthly income is $600/20% = $3,000.
Pair 2 is true if Jeff's monthly income is $1200/10% = $12,000.
Both pairs can be true if Jeff's monthly income increased by a factor of 4 in the 20 years from 1990 to 2010.
Obviously, Jeff spent more on housing in 2010. (Fortunately for Jeff, that larger expenditure was a smaller fraction of his income.)
The answer is A only 5 lines of symmetry
1) Subtract 2m
2) Subtract m
3) Add 1
4) Subtract 2
5) Add 2
6) Subtract 1
The mean can be found by adding the two numbers and dividing by 2
let the second number be y
(x + y)/2 = 1/2x + 1
solve for y
multiply each side by 2
x + y = 2(1/2x + 1)
distribute
x + y = x + 2
subtract x on both sides
y = 2
ANSWER: the second number is 2
