1) (n+5)-(n-8)=n+5-n+8=13
2) 3x⁴-5x+7x²-8x⁴+5x=-5x^4+7x²
3) (c³-2)² =c^6-4c³+4
(2b+3)³ =8b³+36b²+54b+27
(3c³-2a²)³=27c^9-54c^6a²+36c³a^4-8a^6
4) (19+2x)-(5x-11)=25
19+2x-5x+11-25=0
3x=5
x=5/3
5) (-2m⁵n‾³)² =4m^10n^-6
5³:5 =5²=25
(3²)‾⁴:3‾¹⁰.=3^-8 : 3^-10=3²=9