F.1 maths help!!!急!!!show step!!

(1) [(6a^2)/(3a)^2]^3
=(12a^2/9a^2)^3
=(4/3)^3
=64/27

(2) -48p^5/[(3p^2)(-2p)^3]
=-48p^5/(-24p^5)
=2

(3) (9x^2y^4)^3/(3xy^5)^2
=729x^6y^12/8x^2y^10
=729/8x^4y^2

(4) 8(x-2)+4(x+1)=3(x+5)
8x-16+4x+4=3x+15
12x-12=3x+15
12x-12-3x+12=3x+15-3x+12
9x=27
9x/9=27/9
x=3

(5) (x+8)/(28-5)=y+1
(x+8)/23=y+1
x+8=23y+23
x+8-8=23y+23-8
x=23y+17

(6)Alex swam a 50m journey with breaststroke,freestyle and backstroke.He swam(2f-7)m with breastroke and (3f-2g+1)m with freestyle.Express,in an algebraic expression,the distance he swam using backstroke.

=50-(2f-7)-(3f-2g+1)
=50-2f+7-3f+2g-1
=50+7-1-2f-3f+2g
=56-5f+2g