Let amanda's age be x and her dad's age be y.
Amanda’s dad is twice as old as she, therefore 2x=y
The sum of their ages is 66, therefore x+y=66
x+y=66
2x=y,
substitute.
2x+x=66
3x=66
Divide.
x=22.
plug it back in, 22+y=66, y=44.
Amanda's age is 22 and her dad's age is 44.