Final answer:
Raymond mowed 18 out of 30 lawns, so the fraction of lawns he mowed is 3/5.
Step-by-step explanation:
To find the fraction of lawns Raymond mowed, we can divide the number of lawns Raymond mowed by the total number of lawns mowed by both Raymond and Andrew.
In this case, Raymond mowed 18 lawns, and the total number of lawns mowed is 30.
The fraction of lawns Raymond mowed is therefore 18/30, which can be simplified to 3/5.