John's mother is 5 times as old as John is. Three years ago, she was 9 times his age. What are their present ages?
Have a think.
Let John's age be
His mother's age will then be
So three years ago she was nine times his age...
The on the left side represents 3 years ago, you also have to do it on his mother's age. Since she is nine times the age just multiply the whole side by 9.