A certain number is added to 9 the result is 5 - the same number what is the number​

Question 5 spring semester final exam math evaluate

Me! i really need to get this right before 9. prove the divisibility of 7^6+7^5-7^4 by 11. use factoring so you get a number times 11. just tell me the number. i need this done asap

Which of the following is the best first step in solving the equation below? 4+2㏒³x=17