Answer:
Alissa's current age = 4
David's current age = 16
Step-by-step explanation:
if say Alissa is x years old then David is 4x years old
in 8 years Alissa will be x+8, and David 4x+8 and that's twice as Alissa's age therefore:
2×(x+8)=4x+8
2x+16 = 4x+8
16-8=4x-2x
8=2x
x=4
