Question 501020
Mom's age is 20+x
Mom's age ten years ago is 20+x-10 = 10+x
Twice the daughter's age ten years ago is 2(x-10)

hence
10+x = 2(x-10) = 2x-20 
10+x = 2x-20  add 20 to both sides of the eqn.
30+x = 2x     subtract x from both sides of the eqn
30 = x

sothe daughter is 30 years old now and the Mom is 30+20 = 50 years old now