Answer:
Cost of a roll of plain wrapping paper = $6
Cost of a roll of shiny wrapping paper = $20
Step-by-step explanation:
Let [tex]x[/tex] denotes cost of a roll of plain wrapping paper and [tex]y[/tex] denotes cost of roll of shiny wrapping paper.
Jack sold 5 rolls of plain and 8 rolls of shiny for a total of $190.
[tex]5x+8y=190\,\,\,(i)[/tex]
Beth sold of 5 rolls plain and 3 shiny for a total of $90.
[tex]5x+3y=90\,\,\,(ii)[/tex]
Subtract (ii) from (i).
[tex]8y-3y=190-90\\5y=100\\y=20[/tex]
Put [tex]y=20[/tex] in (ii)
[tex]5x+3(20)=90\\5x+60=90\\5x=90-60\\5x=30\\x=6[/tex]
Therefore,
Cost of a roll of plain wrapping paper = $6
Cost of a roll of shiny wrapping paper = $20