用十進數表示下列各式^^

(a)8*10+6*10^2+1
=6*10^2+8*10^1+1*10^0
=681(10)
(b)4*10^2+5*10^3
=5*10^3+4*10^2+0*10^1+0*10^0
=5400(10)
(c)3*100+2*10000+10
=2*10^4+0*10^3+3*10^2+1*10^1+0*10^0
=20310(10)

solve here anyway though somebody already answered.
just for your reference:
abcdefg (10) = g(10^0) + f(10^1) + e(10^2) + ... + a(10^6)
abcdefg (x) = g(x^0) + f(x^1) + e(x^2) + ... + a(x^6)

8a.
8 x 10 + 6 x 10^2 + 1
= 80 + 600 + 1 = 861
8b.
4 x 10^2 + 5 x 10^3
= 400 + 5000 = 5400
8c.
3 x 100 + 2 x 10000 + 10
= 300 + 20000 + 10 = 20310