đầu tiên được `1/15  tiếp theo kết quả được`1/4`  và

  được `5`

a: =45/60+24/60+15/60=84/60=7/5

b: =(47/15-2/15)+(40/17-6/17)=3+2=5

4⁶ . 9⁵ + 6⁹ . 120 / 8⁴ . 3¹² - 6¹¹

= ( 2² )⁶. ( 3² ) ⁵ + (2 . 3 ) ⁹ . 2³ . 3 . 5 / ( 2³ ) ⁴ . 3¹² - ( 2 . 3 ) ¹¹
= 2^12.3^10+2^9.3^9.2^3.3.5 / 2^12.3^12-2^11.3^11
= 2^12.3^10+2^12.3^10.5 / 2^11.3^11.(2.3-1)
= 2^12.3^10.(1+5) / 2^11.3^11. (6-1)
= 2^12.3^10.6 / 2^11.3^11.5
= 2^13.3^11 / 2^11.3^11.5
= 2^2/5
=4/5

\(\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}=\frac{2^{12}.3^{15}+2^9.3^9.8.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{15}+2^{12}.3^{10}.5}{2^{11}.3^{11}\left(6-1\right)}\)

\(=\frac{2^{10}.3^{10}\left(2^2.3^5+2^2.5\right)}{5.6^{11}}=\frac{6^{10}\left[4\left(243+5\right)\right]}{6^{10}.30}=\frac{4\left(243+5\right)}{30}\)

\(=\frac{992}{30}\)