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