Let's say x to Kara's age since Joseph is 18 years older than her, his age is x+18.
12 years ago, Kara's age was x-12 and Joseph's age was x+6. And Joseph's age was 4 times as hers. So :
[tex]x+6=4(x-12)\\ x+6=4x-48\\ x+48+6=4x\\ x+54=4x\\ 54=4x-x\\ 54=3x\\ \frac { 54 }{ 3 } =x\\ x=18[/tex]
Kara is 18 years old and Joseph is 18+18= 36 years old
