This property indicates that when there are or more digits in these operations, the result does not depends on the way the terms are grouped. Therefore:
[tex]\begin{gathered} 3+(4+5)=(3+4)+5 \\ 3+9=7+5 \\ 12=12 \end{gathered}[/tex]therefore, the answer is the last option 3+ (4+5) = (3+4) +5
