It will be C cause you divid 15 and 6
Using simultaneous equation,
a=-1, b=1, x=1, y=0
OR
a=1, b=-1, x=1, y=0.
Even
means ends with 0,2,4,6,8
adds to 10
the last number cannot be 0 because the first cannot be add to 10
it can be
8xx2
6xx4
4xx6
8xx2
where x is any whole number you want