So for this, you might want to set up some equations.
The mom's variable is m and the daughter's is d. Â
So now is it m=2d
And twenty years ago it was m-20=4(d-20)Â which is the same as m-20=4d-80.
Simplify so it is m=4d-60. Now, plug it in as m in the first equation.Â
4d-60=2d      2d=60    d=30 Â
Now, we know that the mom must be 60 and the daughter 30 years old.