1) 24 - x = 15; x = 24 - 15; x = 9;
2) 13 + x = 37; x = 37 - 13; x = 24;
3) x - 56 = 41; x = 41 + 56; x = 97;
4) x - 391 = 9; x = 9 + 391; x = 400;
5) 152 + x = 257; x = 257 - 152; x = 105;
6) 392 - x = 22; x = 392 - 22; x = 370;
7) 517 - x = 420; x = 517 - 420; x = 97;