Before it started to rain, Bobby cut 18

There is not enough information provided to determine which statement is true.

To determine which statement is true, we need to compare the amounts of grass cut by Bobby and Danny to the size of the entire yard.

Let's assume that the entire yard represents 100% of the grass.

Bobby cut 18% of the grass, and Danny cut 15% of the grass.

To find out if they were able to cut the entire yard, we can add the percentages they cut:

18% + 15% = 33%

Since the sum of the percentages (33%) is less than 100%, the statement "Both boys were not able to cut the entire yard" is true.

The statement that is true is: "Bobby cut more grass than Danny."