Year 7 - Q2.5.10
20376
A machine multiplies an input by a positive whole number \(a\), then adds a positive whole number \(b\). You know \(a+b=9\), and input \(4\) produces output \(24\). Find the rule, then find the input that produces \(39\). Show that no other allowed rule works.
Hint
List the positive pairs that sum to nine and test the given input.