Specified variable a = 3b - c, for b
a = 3b -c //we move 'b' to left sidea - 3b = - c // we move 'a' to right side-3b = -a - c // we multiply by -13b = a + c // we devide by 3b = (a + c ) / 3 other version => b = (1/3)a+ (1/3)c