An old man said, "add 17 to my age and divide it by 4. Subtract 15 and multiply it by 10. It happens to be 100 years old.",

An old man said, "add 17 to my age and divide it by 4. Subtract 15 and multiply it by 10. It happens to be 100 years old.",

100 divided by 10 = 10, then 10 + 15 = 25. In use 25 * 4 = 100, in use 100-17 = 83. Oh no?