Answer:
8 minutes.
Explanation:
Time taken to upload 12 photographs from a smartphone to a computer = 3.5 minutes
Time taken to upload that 12 photographs from computer to a website = 1.25 minutes.
∵ The time taken for 12 photographs to upload from smartphone to a computer then to a website = 3.5 + 1.25 = 4.75 minutes.
∴ The time taken for 1 photograph to upload to a website =

∴ Time taken to upload 20 photographs from a smartphone to a computer then to a website =

= 7.916 ≈ 8 minutes.
It will take 8 minutes to upload 20 photographs.