For each step below, choose which property is being applied to create an equivalent expression.

2+(9+1)\displaystyle {2}+{\left({9}+{1}\right)} = 2+(1+9)\displaystyle {2}+{\left({1}+{9}\right)}       

                     = (2+1)+9\displaystyle {\left({2}+{1}\right)}+{9}  

                     = (1+2)+9\displaystyle {\left({1}+{2}\right)}+{9}  

                     = 1+(2+9)\displaystyle {1}+{\left({2}+{9}\right)}  

                     = 1+(9+2)\displaystyle {1}+{\left({9}+{2}\right)}  

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