Can anyone me with these answers, show work if you can if not that's ok! (only odd questions )

21.
pemdas
simplify inside parenthes to get
80-(3)^3
exponents
80-27
53

23.
hum, very interesting
6^4=(2*3)^4=(2^4)(3^4)=(2^4)(3^2)(3^2)
so therefor the 6^4 divided by 3^2 is actually (2^4)(3^2)(3^2)/(3^2) which simplifies to (2^4)(3^2)
now we got
(2^4)(3^2)/9 or (2^4)(3^2)/(3^2) which simplifies to 2^4 or 16

25.
subsitute
(4+8)^3
simplify inside parenthaes
12^3
1728

27.
(st)^2=((4)(8))^2=(32)^2=1024

29.
(8-4)^5
4^5
1024

31.
2(4)(8)^2-(4)^2
2(4)(64)-16
512-16
496

33.




2(1728)+2
3456+2
3458

35.
momentum=mv
when m=1000kg and v=15m/s, then momentum=15000kg m/s
when m=1000kg and v=20m/s, then momentum=20000kg m/s
when m=1000kg and v=25m/s, then momentum=25000kg m/s