Bonsoir,
B=7(20)_7(5)
[tex]B=\dfrac{7^{20}}{7^5}=7^{20-5}=7^{15}[/tex]
C=6(-4)x6(2)x6(-7)
[tex]C=6^{-4}\times6^2\times6^{-7}=6^{-4+2-7}=6^{-9}[/tex]
D=5,5(3)x(5.5(2))-4
[tex]D=5,5^3\times(5,5^2)^{-4}=5,5^3\times5,5^{2\times(-4)}\\\\=5,5^3\times5,5^{-8}=5,5^{3-8}=5,5^{-5}[/tex]
F=35(-5)_7(-5)
[tex]F=\dfrac{35^{-5}}{7^{-5}}=\dfrac{(7\times5)^{-5}}{7^{-5}}=\dfrac{7^{-5}\times5^{-5}}{7^{-5}}=5^{-5}[/tex]