If the snake is now 3 foot 9 inches, we can add up how many inches that is by converting feet to inches. 1 foot=12 inches, so 3 feet is 36 inches. We then add the 9 inches.
36+9= 45
Since the snake had already accomplished being 5 inches at birth, we can subtract 5 from 45.
This gives us 40.
Since the snake was born 4 years ago we divide 40 by 4.
