tolong jawab kak, beserta caranya dikumpul hari ini

diket:
f(x)= 3x+7
h(x)= (x-3)/(x+1)
gof(x)= (3x+7)/(3x+9)

dimisalkan
3x+7= a
3x=a-7
x=(a-7)/3

gof(x)= (3x+7)/(3x+9)
g(a)=(3(a-7)/3 +7)/(3(a-7)/3 +9)
= ((a-7)+7)/((a-7)+9)
= (a)/(a+2)
g(a)= a/(a+2)
g(x)= x/(x+2)

maka:
goh(x)= g(h(x))
= (x-3)/(x+1) : ( (x-3)/(x+1) +2)
=(x-3)/(x+1) : ( ((x-3) + 2(x+1))/(x+1) )
=(x-3)/(x+1) : ( (x-3+2x+2)/(x+1) )
= (x-3)/(x+1) : ( (3x-1)/(x+1) )
=(x-3)/(x+1) * (x+1)/(3x-1)
= (x-3)/1 * 1/(3x-1)
= (x-3)/(3x-1)....

jawaban: B.