tolong yaa bantuin pake cara .thanks

(2,8) dan (4,12)
[tex] \frac{y-y1}{y2-y1} = \frac{x-x1}{x2-x1} = \frac{y-8}{12-8} = \frac{x-2}{4-2} = (y-8) 2 = (x-2) 4[/tex]
2y-16 = 4x -8
2y-4x =8
maka titik (9,a)
2. a - 4.9 = 8
2a -36 = 8
2a = 44
a=22