Question 133376
Let Bob's age = x
And Tim's age = y
then y=4x because (Tim is 4 times as old as Bob is)
y+6=2(x+6)(Six years from now, Tim will be twice as old as Bob will be)
then

4x+6=2x+12
then
2x=6
x=3
and y = 12
Answer: Bob is 3 years now