The selling cost for Stefan bicycle = $114 and
the selling cost of a helmet = $18.
The total cost for Jin is 120% of the money spent.
Let us assume purchasing cost of a bicycle = $x.
Purchasing cost of a halmet = $y.
For bicycle
120% of x is $114
=> 1.20 × x = 114
Dividing both sides by 1.20, we get
x=$95.
For helmet.
120% of y is $18.
=> 1.20 × y = 18.
Dividing both sides by 1.20, we get
y = $15.
$114 - 95 = $19
$18 - 15 = $3.