Tolong dijawab beserta caranya

Diket:
Xa = 6,3
Xb = 7,4
Xab = 7

Ditanya: perbandingan b dan a = ...?

[tex]Xab= \frac{(a.Xa)+(b.Xb)}{n(a)+n(b)} \\\\ 7= \frac{(a.6,3)+(b.7,4)}{a+b} \\\\ 7(a+b)=6,3a+7,4b \\ 7a+7b=6,3a+7,4b\\ 7a-6,3a=7,4b-7b \\ 0,7a= 0,4b \\ \frac{b}{a} = \frac{0,7}{0,4} \\ \frac{b}{a} = \frac{7}{4}[/tex]

Jadi, perbandingan putri : putra = 7 : 4