Answer:
90 minutes
Step-by-step explanation:
let x=amount of time it would take for Shelby to knit the scarf
[tex]\frac{15}{5} =\frac{x}{30}[/tex]
cross multiply
15*30=5x
450=5x
450/5=x
x=90
It would take Shelby 90 minutes to knit a scarf that is 30 inches long.