Question 501020
Let
Present age of mother = m
Present age of daughter = d
Mother is 20 years older then her daughter means if we add 20 years to daughter's age both will be of equal age
m=d+20 .........(1)
Ten years ago means we have to subtract 10 from their present ages
m-10=d-10
then
the mother was twice as old as the daughter
m-10=2(d-10)
m-10=2d-20
m=2d-20+10
m=2d-10...........(2)
Plug in the value of m from (1) to (2)
m=2d-10
d+20=2d-10
d-2d=-10-20
-d=-30
Multiply by (-1) both sides of the equation
(-1)(-d)=(-1)(-30)
d=30
Now plug in the value of d in (1)
m=d+20 .........(1)
m=30+20
m=50

Mother is 50 and daughter is 30 years old