85 PLATES + 102 CUPS COST $13.6
20 PLATES + 24 CUPS COST $_____
85 + 102=187 total of plates and cups.
$13.60/187=.0727cents the average cost of a plate and a cup.
20 + 24=44 X .0727=$3.20
Both the number of plates and the number of cups have beeen reduced by the same factor....i.e 20/85 = 24/102 , (4/17) so the price will be reduced by the same factor or 4/17 x 13.6 = $3.20
