Answer :
Lennie used the associative property.
The associative property basically shows that in any order the parenthesis are grouped, you will get the same number.
For example: 19+(11+37)= (19+11)+37=67

Lennie used the associative property.
The associative property basically shows that in any order the parenthesis are grouped, you will get the same number.
For example: 19+(11+37)= (19+11)+37=67