520 : (515.6+515.19)
=520:[515.(6+19)]
=520:[515.25]
=520:[515.52 ]
=520:[515+2 ]
=520 : 517
=520-17
=53
=125
chúc bạn học tốt
=5^20:[5^15(6+9)]
=5^20:[5^15.15]
=5^20.[1/5^15.1/15)
=5^20.1/5^15.1/15
=5^20:5^15.1/15
=5^20-15.1/15
=5^5.1/15
=5^5/15
=5.5^4/5.3
=5^4/3
(=625/3)