Expressions equivalent to 3(1+x)+7 is x+10
Answer:
7
Step-by-step explanation:
We want to find the number 4-digit of positive integers n such that removing the thousands digit divides the number by 9.
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Let the thousands digit be 'd'. Then we want to find the integer solutions to ...
n -1000d = n/9
n -n/9 = 1000d . . . . . . add 1000d -n/9
8n = 9000d . . . . . . . . multiply by 9
n = 1125d . . . . . . . . . divide by 8
The values of d that will give a suitable 4-digit value of n are 1 through 7.
When d=8, n is 9000. Removing the 9 gives 0, not 1000.
When d=9, n is 10125, not a 4-digit number.
There are 7 4-digit numbers such that removing the thousands digit gives 1/9 of the number.
Answer: Choice A
Proof:
Replace x with 1 and y with 2. This is because (x,y) = (1,2) so x = 1 and y = 2.
Doing both replacements and simplifying leads to...
2*x - y = 0
2*1 - 2 = 0
2 - 2 = 0
0 = 0
That confirms (x,y) = (1,2) is a point on the line.
It confirms (1,2) is a solution to the equation.
