If 7 spiders make 7 webs in 7 days, then 1 spider will make 1 web ?

Let the required number days be x.
Less spiders, More days (Indirect Proportion)
Less webs, Less days (Direct Proportion)
Hence we can write as,

• 1 x 7 x x = 7 x 1 x 7

x = 7.