Question 16601
N=3
First you might want to convert the question word to word. 
Seven times a number is the same as 12 more 3 times the number.
 7      X     n         =           12  +   3   X      n
Now you can move the like terms to one side. You should subtract 3n from each side.
 7n - 3n = 12+3n - 3n.
=    4n  = 12
Divide 4n by 4 so this side will only be left with variable it self.Do the same with 12.
=  4n/4 = 12/4
=   n   =  3