Proposition: 7.39: Least Number with Three Given Fractions
(Proposition 39 from Book 7 of Euclid's “Elements”)
To find the least number that will have given parts.
 Let $A$, $B$, and $C$ be the given parts.
 So it is required to find the least number which will have the parts $A$, $B$, and $C$ (i.e., an $A$th part, a $B$th part, and a $C$th part).
Modern Formulation
If $A=\frac 1D,$ $B=\frac 1E,$ $C=\frac 1F,$ and $G=\operatorname{lcm}(D,E,F)$ is the least common multiple of these numbers with $D=\frac G{d},$ $E=\frac G{e},$ $F=\frac G{f},$ then $A=d/G,$ $B=e/G,$ and $C=f/G.$
Table of Contents
Proofs: 1
Thank you to the contributors under CC BYSA 4.0!
 Github:

 nonGithub:
 @Fitzpatrick
References
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"
Adapted from CC BYSA 3.0 Sources:
 Prime.mover and others: "Pr∞fWiki", https://proofwiki.org/wiki/Main_Page, 2016