Finding the share of Marbles through Simple Arithmatic Fraction

Question

My 5th grader is practicing simple arithmatic fractions. He stumbled upon a question and now its troubling me too. I can't seem to solve the question without the help of Algebra which I can not explain to my kid without a proper introduction. Will appreciate if someone can give a hint on solving it without involving Algebraic expressions. Question goes as follows:

Peter, John and Mary share 78 marbles. Peter takes $\dfrac{1}{3}$ of the marbles and John takes thrice as many as Mary. Find the number of marbles John takes.

Edit: Apparently the question has been marked-down due to the absence of my attempt. So here it goes:

$\dfrac{1}{3}$ of 78 is 26. So Peter took 26 away from 78. 52 remains to distributed among John and Mary. From the given info John (J) keeps 3 times of the Mary's(M) share so J=3M. We know J + M = 52. We can substitute J in the equation that will become 3M + M = 52, therefore M = $52 \div 4$ $\implies$ M = 13. As J=3M, therefore J = $3\times 13$ which is 39. But this involves Algebra which I want to avoid explaining my kid at this moment.

Answer 1

To a 5th grader who cannot make algebraic equation, you can explain in steps -

1. Remove $\frac{1}{3}$ of 78 marbles first and give to Peter
2. Then make four equal parts with the remaining as one of them is taking three parts and the other is taking one part.
3. Once we have made four parts, give one part to Mary and three parts to John.

There is a nice one you can try to explain to a 5th grader without algebraic equations:

There are total of 45 soldiers and horses. If there are 120 legs in total, how many soldiers and horses?