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: -623 and 326
Add: 258 and -473
Add: -622 and -254
Subtract: 4 from -7
Subtract: -8 from -2
Subtract: 329 and -124