Answer: That number is 16.
Step-by-step explanation:
n + 7 = 2n- 9 n represents the number now solve the question 
 + 9 +9 add 9 to both sides 
n + 16 = 2n subtract n from both sides 
-n -n 
 16= 1n Divide both sides by 1 
n= 16 
Check: 16 + 7 = 2(16) - 9 
 23 =23