The federal minimum wage is $7.25 per hour with overtime for all hours worked over 40. An 18 year old is considered an adult and can work any hours.
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Texas follows the federal minimum wage at $7.25. An 18 year old can work unlimited hours although if your job falls within the provisions on the FLSA (you can read more about FLSA provisions at http://kielichlawfirm.com/employment-law/wage-overtime-claims/) then you must be paid one and a half times your regular rate of pay for each hour above forty hours in each work week.
The age of majority is 18, which makes you an adult. Therefore, as an adult, you can work any scheduled hours/days. However, as correctly stated by the other attorneys, if you work over 40 hours in a week, then you are entitled to receive your hourly pay at time and a 1/2 for any overtime (hours you work beyond the 40). For example, if you make $8.00 per hour and work 50 hours a week, then you should receive $12.00 per hour for those 10 hours that you worked over the 40. If you need any additional explanation(s), you can go to the Texas Workforce Commission site.
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