Răspuns :

Răspuns:

((2x+7)-13)=12

2x+7=12+13

2x+7=25

2x=25-7

2x=18

x=18÷2

x=9

((2x+13)-11)=6

2x+13=6+11

2x+13=17

2x=17-13

2x=4

x=4÷2

x=2