Answer: n=58
Explanation:
 
7(n-7)=3(2n+3) 
 
We move all terms to the left: 
 
7(n-7)-(3(2n+3))=0 
 
We multiply parentheses 
 
7n-(3(2n+3))-49=0 
 
 
We calculate terms in parentheses: -(3(2n+3)), so: 
 
3(2n+3) 
 
We multiply parentheses 
 
6n+9 
 
Back to the equation: 
 
-(6n+9) 
 
 
We get rid of parentheses 
 
7n-6n-9-49=0 
 
We add all the numbers together, and all the variables 
 
n-58=0 
 
We move all terms containing n to the left, all other terms to the right 
 
n=58