Concept:Setting up and solving a linear equation based on the given age relationship.Explanation:Let's assume Devasena's current age is $x$ years.As per the problem, after 12 years, her age will be $x + 12$ years.The problem states that this future age will be four times her present age. So, we can write the equation:$x + 12 = 4x$Now, we solve this equation for $x$:Subtract $x$ from both sides:$12 = 4x - x$$12 = 3x$Divide both sides by 3:$x = \frac{12}{3}$$x = 4$Therefore, Devasena's present age is 4 years.Answer:4 years