Question

Jenny bought 5 pens for $3 at this rate, how much will she spend on 10 pens

Answer 1

She will spend $6 five is $3 and if you add 5 more, it will be the same as adding $3 so 10 pens will be $6

Answer 2

Most likely, she will spend $6 on 10 pens. 
This is because if you multiply 5x2 you get 10, the question is asking for the price of 10 pens.
Then you would multiply 3x2 because we multiplied 5 by 2. 
You would get 6, this is the answer.
Hope this helped!