Răspuns:
x = 1
Explicație pas cu pas:
[tex]1+{2*[3+(4+x):5]-6}*7= 15\\\\{2*[3+(4+x):5]-6}*7 = 15 -1\\\\2*[3+(4+x):5]-6 = 14 : 7\\\\2*[3+(4+x):5]-6 = 2\\\\2*[3+(4+x):5]=2+6\\ \\2*[3+(4+x):5]=8\\ \\3+(4+x):5 = 8:2\\\\3+(4+x):5 =4\\\\(4+x):5 =4-3\\\\(4+x):5 = 1\\\\(4+x)=1*5\\\\4+x=5\\\\x = 5-4\\\\\boxed{x=1}[/tex]
