a)
((3/5)⁻² - (6/7)⁻¹)⁻¹= ((5/3)²- (7/6))⁻¹=
=(25/9 - 7/6)⁻¹= (50/18 - 21/18)⁻¹= (29/18)⁻¹= 18/29
b)
(0,81⁻½ - 0,064^⅓)*8⁻¹= ((81/100)⁻½ - (64/1000)^⅓)*(1/8)=
=((100/81)^½ - (4/10))*(1/8)=((10/9)-(2/5))*(1/8)=
=((50/45)-(18/45))*(1/8)=(32/18)*(1/8)=4/18=2/9
c)
7^¾ *³√(7)⁵=7^¾ *7^⁵/³= 7^(¾⁺⁵/³)=7^(⁹/¹² ⁺ ²⁰/¹²)=
=7^²⁹/¹²
