Part a) we know that it takes 7 hours for Isabella to rake leaves so 7 hours---------------> 100% 1 hours---------> x x=100/7-----> 14.29% job/hour--------> this is the rate or 0.1429 job/hour
Matthew can work three times as fast so 14.29*3-----> 42.87% job/hour-------> this is the rate or 0.4287 job/hour
