Tony is required to file a tax return because Gail can claim him as a dependent and his income is over $4200.
Step-by-step explanation:
The income of the child determines whether he must file taxes or not. His age does not determine it. So even if Tony is only seventeen year old, he must file his taxes.
Tony has to file the taxes because his earned income for the year is more than $6350 and his unearned income which is in the form of social security benefits is more than $1050, so he has to file his taxes.