a ) 538-x+821 = 1798
538 - x = 1798 - 821
538 -x = 977
-x = 977- 538
-x = 439
x = - 439
b ) x-4281 + 3584 = 30000
x- 4281 = 30000- 3584
x-4281 = 26.416
x= 26.416 + 4281
x = 30.697
c ) 2030 + x - 13521 =8213
2030 + x = 8213+13521
2030 + x = 21734
x = 21734 - 2030
x = 19704