[tex]a)1275 = 1 \times 1000 + 2 \times 100 + 7 \times 10 + 5 \times 1[/tex]
[tex]b)5001 = 5 \times 1000 + 0 \times 100 + 0 \times 10 + 1 \times 1[/tex]
[tex]c)7040012 = 7 \times 1000000 + 0 \times 100000 + 4 \times 10000 + 0 \times 1000 + 0 \times 100 + 1 \times 10 + 2 \times 1[/tex]
[tex]d)8700001 = 8 \times 1000000 + 7 \times 100000 + 0 \times 10000 + 0 \times 1000 + 0 \times 100 + 0 \times 10 + 1 \times 1[/tex]