1. 3 852 - a + 1650 = 4 257
3 852 - a = 4 257 - 1650
3 852 - a = 2 607
a= 3 852 - 2 607 =1 245
2. a + 3 649 - 2 138 = 4 587
a + 3 649 = 4 587 + 2 138
a + 3 649 = 6 725
a = 6 725 - 3 649
a = 3076
3. a - b + c = 8 110
a + b = 6 150
c = 8 110 - 6 150 = 1 960
b = 6 150 - 1 960 = 4 190
a = 8 110 + 1 960 + 4 190 = 14 260