Divide the actual building's measurements by the replica's measurements.

The measurements of the actual building are divided by
20 not 12.
The crew member's calculation is
incorrect.
Sajia can sell 21 books she can sell if she comes back on sunday and the required inequality is 
<em><u>Solution:</u></em>
Given that Sajia has 30 Books in her library
She sold 9 books at the thrift store on Saturday
To find: We have to write and solve an inequality to determine number of more books she can sell if she comes back on sunday
Let "x" be the number of more books she can sell if she comes back on sunday
<em><u>We can write a inequality as:</u></em>


Now moving 9 from L.H.S to R.H.S we get,

On solving 30 - 9 = 21,

So Sajia can sell 21 books she can sell if she comes back on sunday
I believe it is the first one
Answer:
The first number is 20, the second one is 11
Step-by-step explanation:
Let the first number be x and the second number be y
Since it says "9 is the difference between two numbers", the first equation will be x-y=9
It also says that "their sum is 31". That means the second equation will be x+y=31
here are the two equations:
x-y=9
x+y=31
You can solve this any way you like, but I'll show elimination
add the two equations
x-y=9
x+y=31
2x=40
divide by 2
x=20
Substitute 20 as x in one of the equations
20+y=31
subtract 20 from both sides
y=11
That means the two numbers are 20 and 11
Hope this helps!