a, 82-(15+x)=72

         15+x=82-72=10

              x=10-15

              x=-5

 b,(x-9).(x+2)=0

=>x-9=0 hoặc x+2=0

nếu x-9=0

=>   x  =0+9

=>   x  =9

nếu x+2=0

=>    x  =0-2

=>    x  =-2

vậy x=9 hoặc x=-2

tick nha

I have many dream, and they are all big dreams. But among them, I want to be a teacher. In Vietnam-my country has many poor village.Children here can't go to school so, i want to come here and teach them for free. If I can do it, I will help the children expand their knowledge and become good people. Especial, they will contribute to build and protect their hometown and ourm country.