Jill is picking up everyone's waterbill so she is paying $60 plus $125 (being half of the water bill) so that comes out to $185.
D=185 in this case
Ron is paying for 1/3 of the rent plus the other half of the water bill. That comes out to 1/3R+125.
A=1/3R+125
And then Jack is paying for Jill's rent as well as his own. That is 2/3 of the rent.
C=2/3R
and then the choice not used is the 'no match' option. Hope this helps :)
