Instead of doing it for you, I'm changing all the numbers so
you can do yours exactly the same way I did this one step by step.
I'm changing it to this problem:

We know that the terms are between 329 and 843, so we write:



Subtract 7 from all three sides



Divide all three sides through by 9



Since n is an integer,



There are 92 integers 1 through 92.

We can't use the first 35 integers 1 through 35,

So there are 92-35 or 57 terms between 329 and 843 of 
an arithmetic sequence 9n+7

Now you do yours exactly the same way step by step.

Edwin