Answer:
$250
Explanation:
Total money he has - $500
He buy a bike for - $200
500 - 200 = 300
Balance - $300
10% tax
10 x 300/100 = 30
300 - 30 = 270
He payed $`20 extra
170 - 20 = 250
Balance = $250
He had $250 balance in his pocket money
Hope you understand
:-)