Answer :

[tex]x-Luke\ marbles\\\\2x-Tom\ marbles\\\\x+2x=39\\\\3x=39\\\\x=39:3\\\\x=13\\\\2x=2(13)=26\\\\Answer:Tom\ have\ 26\ marbles.[/tex]
Devide the marbles with 3
because tom : luke is 2 : 1
And 2+1=3

39/3=13

So tom's marbles = 2 x 13 = 26
And luke's marbles= 1x 13= 13