I tried to multiply the equation by a then b then c... I don't know please help by showing the steps I am very lost

Determine a+b+c
25/84=1/a+1/an+1/abc

2 answers

Sorry it was supposed to be
Determine a+b+c
25/84=1/a+1/ab+1/abc
It's hard to explain.

Because of that in google type:

CRUX MATHEMATICORUM Contest Corner Problem CC210

When you see list of results click on:

There are exactly two positive integer triples (a , b , c) such that , 25/84 ...

and read answer.