>5 * 2 + 1 = 10
>2 + 1 * 5 = 15
>
>change the order of operations and the result changes The - in 5 - 2 is NOT the same operation as the - in -2.

what are you doing? you cannot to like up. you can do that:

5*2+1=11

1+5*2=11

you can change -,+ . you cannot mix -,+,*,/