18+27=45
factors of 18 are 1,2,3,6,9
factors of 27 are 1,3,9
gcf=9
9x5=45
I'm not positive if this is the answer. I'm a little confused about "another sum". I'm not sure if its asking for another factor of the two numbers or just another number. But I think what I did is right. I'm sorry if I'm wrong.