Odds and evens

Cross out one whole row and one whole column in each grid.

a. The sum of the two numbers in each remaining row and column must be even.

a-6 b. The sum of the three numbers in each remaining row and column must be odd.

Age 11-14

Double up

Three friends play a game of cards. They each start with a different number of counters.

After each round of the game, the loser has to use their counters to double the number of counters held by the other two players.

After three rounds, each player has lost one round, and each has 24 counters.

How many counters did each player start with?