We don't have any details about the walls or the room, so let's use algebraic symbols ,for the relevant dimensions. There are four walls so that suggests a rectangular room of height H. If the length of the room is L and the width W (W<L). Let's also assume that there's one door and one window. Let's also assume that neither the door nor the window are in the wall that's to be painted. A door is usually about 0.9m wide and 2m high (including the frame) and let the window have an area A m2. The area of the door is 1.8m2. The combined area of the door and window=1.8+A m2.
The combined areas of the three walls that are going to be papered is 2LH+WH-(1.8+A) m2. The smaller wall has area WH m2. The number of rolls of paper needed=(2LH+WH-(1.8+A))/5.
The number of tins of paint needed=WH/40.
EXAMPLE
L=6m, W=4m, H=2.5m, A=2m2.
Wallpaper=(15+10-(1.8+2))/5=21.2/5=4.24, so 5 rolls would be needed. This would be sufficient even if the door were to be wallpapered.
Paint=10/40=¼ 4L-can. So a 1L-can would be sufficient for one wall (area=10m2).
Substitute your own values for L, W, H and A and see how much paper and paint you would need.