Math Riddles

Question: someone came into my shop and stole 100 dollars from the register without my knowledge. the person came back 5 minutes later with the same 100 dollars and bought 70 dollars in items and i gave him back 30 dollars change. How much did i lose?

Question: I'm 10 years old my brothers half my age now I'm 100 years old how old is my brother now?

Question: A son's age is the age of his dad's age's digits added together. The son is not nine or older. The dad is of legal age. The dad's age doesn’t end in a zero, and is more than twenty, but less than twenty-five. How old is the dad, and how old is the son?

Question: Can you find the missing number in the below series? 43, 8, 38, 9, 34, 11, _, 14

Question: How is 2+2 four, 3+3 eight, and 7+7 triangle?