Given: o is the midpoint of line mn
om=ow
prove: ow=on

Given:
O is the midpoint of line MN
OM = OW

To prove:  OW = ON

Statement                                 Reason
1> OM = OW  > Given
2> OM = ON > O is the midpoint of line MN
                                                           i.e Point O bisects line MN
3> OM = OW > From statement <1>
4> ON = OW  > OM = ON (Statement <2>)
     OW = ON
              
                                                                    proved!!