Peter buys three packets of marbles, each containing 8 marbles. in his first marbles match,
he loses 3 marbles. in his next match, he wins 7 marbles. he then bets half of his marbles on
the outcome of a soccer match, and loses. he plays another marble match and wins 5 marbles.
finally, he bets all of his marbles on a netball match and wins, doubling his number of marbles.
write a numerical expression for the number of marbles he ends up with