so assuming that youmeans there were 35 MORE rose plants than sunflower seeds, then
Rose:Sunflower =8:3
rose=sunflower+35
therefor
8 units=rose
3 units=sunflowers
rose-35=sunflower
8unit-35=3unit
5unit-35=0
5unit=35
therefor
35=5unit
divide by 5
7=1unit
so 8 units of roses
7 times 8=56
3 units of sunflowers
3 times 7=21
rose=56
sunflower=21