Question 297349
This is one reason that many teachers don't like "cross multiplying"
Cross multiplying is a short cut to this
Multiply both sides by 7+2n
Multiply both sides by 18
In cross multiplying you just remove the denominators and multiply the opposite numerator by the denominator

a/b=c/d
multiply c*b and a*d
Multiply the numerator on one side by the denominator on the other side.
Do it again with the other side.
So in the end you should have 
(7-2n)*18 = 1*(7+2n)