Add: -13 and 15
-13 and 15 (-13) + 15 = 2
Add: 13 and 15
Add: 13 and -15
Add: 259 from 214
Add: -528 and -243
Add: -622 and -254
Subtract: 5 from 8
Subtract: -5 from 8
Subtract: 4 from -7
Subtract: -78 from -12
Subtract: -222 from 0