1+1=
2
20-20=
0
10x10=
lOO
20+20=
40
99+2=
101
290-91=
199
100x2=
200
40-19=
21
300+200=
500
1000-998=
100x3=
300
60x2=
120
400+501=
901
100-91=
9
100x4=
400
20-1=
19
700+301=
1001
1000-1001=
-1
1000x9=
9000
201+109=
310