Question 826195
Let x - be the age of Lori
    2x - be the age of Karen

    x+3 - be the age of Lori in 3 years
    2x+3 - be the age of Karen in 3 years

2x+3+x+3=42
3x+6=42
3x=36
x=12

Therefore Lori is 12, and Karen is 24. :)
HOPE THAT HELPS!