Answer:
£25 or £20.10
Explanation:
calculate the area to be painted:
2.1x4.5= 9.45m^2 for each wall
x4= 37.8m^2
area of door= 1.8x0.9= 1.62m^2
subtract the area of the door from the wall area
37.8-1.62= 36.18m^2 to be painted
divide the area by the area that 1L of paint can cover
16.18/12= 3.015 L needed
if 1.5L= £10 then, 3L= £20. she needs 2 cans + an extra 0.015 L- so another can (3 cans total) add price up.
£30- but buy 2 get 3rd 1/2 price, so take £5 off. price is £25
or
calculate price for 0.015L
1.5=£10
divide both sides by 100
0.015= £ 0.10
if 1.5L= £10 then, 3L= £20. she needs 2 cans + an extra 0.015 L
£20+£0.10= £20.10
I DONT KNOW IF THIS IS RIGHT but hope it helps :)