math

1.) a banker has $5.40 dollars in his account he withdraws $4.20 dollars how much is left ?
answer: $1.20

2.) a student gave his teacher $8.60 dollars for a lunch for the field trip the lunch was only $4.40 dollars
how much change does he get back?  answer: $4.20

3.) a man goes to the bank to withdraw $20.80 dollars from his account. he has $20.10 dollars
how  much will be left in his account

ANSWER: $0.20