They would have 2 because is it 10:1 just double it to be 20:2
Substitute 1 for d. d+18=1+18=19
Well think of it like this. lets say your teacher made you do this problem -48 - 10. I would just act like 48 is not an negative and add 10. After that I would put the negative back. So the answer would be -58. :P
