Respuesta :

options for 20:
4*5
2*10
1*20
options for 19:
10+9
8+11
12+7
13+6
14+5
15+4
16+3
17+2
18+1
20+0

so the answer is: 20 and 1 because 20*1 is 20 and 20-1 is 19 (I think)