Răspuns:
2345 + a = 2109
a = 2345 - 2109
a = 236
3489 - a = 1435
a = 3489 - 1435
a = 2054
a - 456 = 5781
a = 5781 + 456
a = 6237
a + 345 + 123 = 6782
a + 468 = 6782
a = 6782 - 468
a = 6314
a × 8 = 56
a = 56 : 8
a = 7
32 : a = 8
a = 32 : 8
a = 4
a : 7 = 345
a = 345 × 7
a = 2415
a : 13 = 585
a = 585 × 13
a = 7605
a × 4 × 2 = 80
a × 8 = 80
a = 80 : 8
a = 10
456 - 234 - a = 2
222 - a = 2
a = 222 - 2
a = 220
15 : 5 : a = 3
3 : a = 3
a = 3 : 3
a = 1
3 × 4 : a = 6
12 : a = 6
a = 12 : 6
a = 2