based on what you described the equation is : -7 < 2x + 1 < 7
like every other problems x is our number, what we are looking for
so let's call the x our ' number ' for better understanding
our number has added one to it's self, but it's not him, we wants our number to be pure, it self, we reduce the our number by 1, so this will append to all numbers
-7 -1 < 2x < 7 -1 ----> -8 < 2x <6
now we just have to do one other thing
we division all the numbers by 2, because our number multiplied by 2
now the equation will be :
-4 < x < 3
so numbers are between -4 and 3, (not -4 & 3 themselves)