Explanation

Let the present age of the baby be x.

After 20 years, the baby's age will be x + 20.

According to the problem, the baby's age after 20 years will be 5 times the present age, so we can set up the equation: x + 20 = 5x

Subtract x from both sides: 20 = 4x

Divide both sides by 4: 5 = x

So, the present age of the baby is 5 years.