Mr. Abbot mowed 1/4 of his lawn. His son mowed 3/7 of the lawn. The first thing to do is get a common denominator, in this case a good one to use is 28. it has to be a number divisible by 4 and 7. 1/4=7/28 3/7=12/28 so now we can see that the son mowed more. now add these two numbers together to get how much they mowed in total (7+12)/28=19/28 of the lawn is mowed. that means 9/28 of the lawn still has to be mowed.