The best way to solve this is by setting up a ratio

450 g = $8.73 therefore, 100 g = ?

450 g / 100 g

=

$8.73 / $x

I like to have my variable (x) on the left side in the numerator,
so, let's flip this

$x / $8.73

=

100 g / 450 g

and now, we solve for x

x =

($8.73)(100 g) / 450 g

x = $1.94

100 g of this cheese will cost $1.94