Math Riddles

Sheilah is now two-thirds of Sally’s age. In six years, Sheilah will be four-fifths of Sally’s age. In 15 years, Sheilah will be seven-eighths as old as sister Sally. If they are both under the age of ten, how old are they now?
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DownUp +50

What is the four-digit number (no zeros) in which the third digit is the number of “winds,” the first digit is one-half of the third, the second digit is double the third and the last digit is one-half the sum of the first three?
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DownUp +31

If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?
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DownUp +5

Rob and Mark live in different parts of town but attend the same high school. Mark left for school ten minutes before Jose and they met in the park. Who was closer to school when they met?
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DownUp +4