Question 215998
3n+2n=7+4n 
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Collect all like terms, in this case that's n, on both side of the =.
5n = 7 + 4n
The equal sign is valid as long as you do the same thing (allowed things, not divide by zero) to both sides.
5n = 7 + 4n
Subtract 4n from both sides
1n = 7
n = 7