Solution: Substitute $ n = 3 $: $ m(3) = 3^2 - 4(3) + 7 = 9 - 12 + 7 = 4 $. \boxed{4}1. A train travels 150 miles in 3 hours at a constant speed. If it continues at the same speed, how many miles will it cover in 5 hours?

["Solution: Substitute $ n = 3 $ in the Formula $ m(3) = 3^2 - 4(3) + 7 = 4 $\n\boxed{4}", "---", "How Train Speed Relates to Distance: A Step-by-Step Solution", "When a train travels 150 miles in 3 hours at a constant speed, calculating its speed is key to predicting future distance. Speed is generally calculated using the formula:", "[\n\ ext{Speed} = \frac{\ ext{Distance}}{\ ext{Time}}\n]", "Using the given values:", "[\nm(3) = \frac{150 \ ext{ miles}}{3 \ ext{ hours}} = 50 \ ext{ miles per hour}\n]", "Now, to find how many miles the train will cover in 5 hours at the same constant speed, use:", "[\n\ ext{Distance} = \ ext{Speed} \ imes \ ext{Time} = 50 , \ ext{mph} \ imes 5 , \ ext{hours} = 250 \ ext{ miles}\n]", "But wait — what if we use a mathematical expression like $ m(n) = n^2 - 4n + 7 $?\nEvaluating at $ n = 3 $:", "[\nm(3) = 3^2 - 4 \ imes 3 + 7 = 9 - 12 + 7 = 4\n]", "While $ m(3) = 4 $ here represents a smaller computed value, real-world train distance depends on actual speed — not abstract function output. So while substitution shows $ m(3) = 4 $, this does not directly model miles traveled over time. For distance prediction, trust the speed formula: $ 50 \ ext{ mph} \ imes 5 \ ext{ hours} = 250 \ ext{ miles} $.", "Final Answer: The train will cover 250 miles in 5 hours."]