the formula for slope is

so just replace y and x for the proper values
The m in y=mx+b stands for the Slope of the equation
5x+x=300
6x=300
x=50
5(50)=250 (Rose)
x=50(John)
Rose has 250 stickers and John has 50, therefore Rose has 200 more stickers than John.
It would be c because this isn't transforming it