$a)5\cdot {10}^3+4\cdot {10}^2+3\cdot {10}^1+2\cdot {10}^0+6\cdot {10}^{-1}+7\cdot {10}^{-2}+9\cdot {10}^{-3}=5432,679$

$b)7\cdot {10}^4+5\cdot {10}^2+2\cdot {10}^0+1\cdot {10}^{-1}+4\cdot {10}^{-2}+0\cdot {10}^{-3}+2\cdot {10}^{-4}=70502,1402$

$c)8\cdot {10}^5+4\cdot {10}^2+2\cdot {10}^0+3\cdot {10}^{-2}+5\cdot {10}^{-4}=800402,0305$

$D)6\cdot {10}^7+2\cdot {10}^1+7\cdot {10}^{-3}+3\cdot {10}^{-5}=60000020,00703$