x-9y+9=0, x=13
a=0
b=13
f(x)=(1/9)x-1
g(x)=(1/6)^(x)
S= ∫ ^(13)_(0)((1/9)(x)-1)-(1/6)^(x)dx=
=((1/9)*(x^2/2) - x -(1/6)^(x)/ln(1/6))|^(13)_(0)=
=(1/18)*(13^2-13-(1/6)^(13)/ln(1/6)-(1/6)^(0)/ln(1/6)=
=[b](169/18)-13+(1/ln6)*(1-(1/6)^(13))[/b]