Answer: ok si cela aide alors ...
Explanation:
While removing the brackets:
1) If there is + in front of them, you simply erase them
a + (b + c) = a + b + c
2) If there is - in front of them, every number that was in brackets changes it's sign
a - (b + c) = a - b - c
By applying the upper rules we do it this way:
7x + [x - (5 + x)] =
7x + ( x - 5 - x) =
7x + x - 5 - x =
7x - 5