Today, Bill is 4 times as old as Jeffery
Let J = Jeffery's PRESENT age
So, 4J = Bill's PRESENT age

In 10 years, Bill will be twice as old as Jeffery.
Since we already know each person's PRESENT age, we know the following...
J + 10 = Jeffery's age IN 10 YEARS
4J +10 = Bill's age IN 10 YEARS

If Bill is twice as old as Jeffrey in 10 years we can write: 4J + 10 = 2(J + 10)
Expand to get: 4J + 10 = 2J + 20
Solve to get: J = 5

So, Jeffery's PRESENT age is 5
Since 4J = Bill's PRESENT age, we know that Bill's PRESENT age = 4(5) = 20

Answer: D