See the posting on Fatimah and Hairu play Congkak to know about Congkak game.
Upper primary school mathematics question UPQ27
Fatimah had some marbles. During a Congkak game, she won 10 marbles and then lost 1/3 of the marbles she had. In a second Congkak game, she lost 12 marbles and had 40 marbles left. How many marbles did she have at first?
Per the model:
Remainder after first game was 2 units = 40 + 12 = 52 marbles
1 unit = 26 marbles
Total marbles she had after won 10 marbles is 3 units = 3 × 26 = 78 marbles
Fatimah had 78 – 10 = 68 marbles at first.