Answer :
The answer to that is always 8, it doesnt matter if you do 1-18 then add 25 or do -18+25 then add one.
If this case You can follow any order. If in the expression appear multiplication or division You must take this into consideration earier thatn subtract/add.
1-18+25=8
You can do it as You want
-17+25=8 or 1+7=8
1-18+25=8
You can do it as You want
-17+25=8 or 1+7=8