arithmetic - the sum of present age of a mother and her daughter is 40 years 4 years ago mothers age was 3 times that of her daughter what is the age of daughter after 4 years - skillgun

Let Age 4 Years ago ,Daughter x & mother 'age be 3x
therefore, present age of Daughter x+4,mother 3x+4
=> x+4+3x+4=40
=> x=8
Present Age of Daughter = x+4
= 8+4
= 12

x=8 is the age of the daughter 4 years ago right?
Therefore present age of daughter , x=8+4=12.
And age of daughter after 4 years, x=12+4= 16.
Please correct me if I am wrong.