1. Stating the problem: We have two wires, one red and one yellow. The red wire is 90 metres long and the yellow wire is 72 metres long. We need to find which wire is longer and by how much. 2. Comparing the lengths: The red wire is 90 metres, yellow is 72 metres. Since $90 > 72$, the red wire is longer. 3. Finding the difference in length: Calculate the difference by subtracting the shorter length from the longer length: $$90 - 72 = 18$$ Thus, the red wire is longer by 18 metres. Final answer: The red wire is longer by 18 metres.