Concept:Understanding the relationship between the perimeter, length, and breadth of a rectangle.Explanation:Let's denote the breadth of the rectangle as $b$ cm and the length as $l$ cm.We are given two pieces of information:1. The length is 3 cm more than its breadth: $l = b + 3$. This can also be written as $l - b = 3$.2. The perimeter of the rectangle is 30 cm.The formula for the perimeter of a rectangle is $P = 2 \times (l + b)$.Substituting the given perimeter, we get $30 = 2 \times (l + b)$.Dividing both sides by 2, we find $l + b = 15$.Now we have a system of two linear equations:Equation (1): $l + b = 15$Equation (2): $l - b = 3$To find the length ($l$), we can add Equation (1) and Equation (2):$(l + b) + (l - b) = 15 + 3$$2l = 18$Divide by 2 to get the length: $l = \frac{18}{2} = 9$ cm.We can also find the breadth by substituting $l=9$ into Equation (1): $9 + b = 15$, which gives $b = 15 - 9 = 6$ cm.The question asks for the length of the rectangle.Answer:9 cm