17. All multiplication and divison must be done before any addition and subtraction. To do the addition first, you would write:
(2+3)x5, which would equal 25
What do you maen by if all four came in a sum? Addition? Then I guess you could just go in any old order. But if there's any subtraction then you'd have to go left to right.
If all 4 appear, then you do all the multiplication and division first throughout the whole sum (depending on brackets etc). It doesnt matter which way round they are done, it should all equal the same (try it!). Then I would write it all out again with the partial sum done, then do the addition and subtraction. Again it doesnt matter which way round.