1)
1000000 : 1000 − 999;
1000000 : 1000 + 1;
420000 − 20000;
28000 : 4 * 100.
2)
800 − 139 * 4 + 244;
234 * 3 : 9;
1000 − 678.

1000000 : 1000 − 999 = 1000 − 999 = 1;
1000000 : 1000 + 1 = 1000 + 1 = 1001;
420000 − 20000 = 400000;
28000 : 4 * 100 = 7000 * 100 = 700000.
800 − 139 * 4 + 244 = 800 − 556 + 244 = 244 + 244 = 488;
$\snippet{name: column_multiplication, x: 139, y: 4}$
$\snippet{name: op_column, sign: '-', x: 800, y: 556, z: 244}$
$\snippet{name: op_column, sign: '+', x: 244, y: 244, z: 488}$
234 * 3 : 9 = 702 : 9 = 78;
$\snippet{name: column_multiplication, x: 234, y: 3}$
$\snippet{name: long_division, x: 709, y: 9}$
1000 − 678 = 322.
$\snippet{name: op_column, sign: '-', x: 1000, y: 678, z: 322}$