Answer:
n=15/2 or n=7.5. (their two versions of the same number. one in fraction form the other in decimal form.)
Explanation:
(n represents 'a number' in this equasion)
3n=5n-15
3n=5n-15
3n-5n=-15 (isolate the variale)
-2n=-15
n=15/2 (a negative divided by a negative is a positive)
n=7.5