The answer for the question is a
The numbers between 30 and 40 whose only factors are one and themselves, also called prime numbers, are 31 and 37.<span> Prime numbers are useful in generating numerical passwords or codes that are difficult to crack. so A) is the answer
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1.) 1+10a-5a
Subtract 5a from 10a
Final Answer: 1+5a
3.) x-9-3x
Subtract 3x from x
Final Answer: -9-2x
5.) 1-4n+2n-1
Subtract 1 from 1
-4n+2n
Add
Final Answer: -2n
7.) 10k-3k
Subtract
Final Answer: 7k
9.) 5r+4-4
Subtract
Final Answer: 5r
