Question

solve this problem fast

Answer 1

$\huge\mathfrak\red{☟︎︎︎ \: \: ᴀɴsᴡᴇʀ \: \: ✍︎}$

y=the sum of the series 1,2,3,4,5,6,7,8,9. Therefore, Sum of required sequence from 1 to 9 is 45.