It would take the kitten 25 days after its birth to triple its weight.
Solution:
kitten weighed 100 grams at birth
And gained 8 grams per day
kitten needed to triple its weigh
Which means, they have to become 3 x 100 = 300 grams
Let "x" be the number of days needed to be 300 grams
Then we can say,
300 grams = 100 grams at birth + 8 grams( number of days)
Thus it would take the kitten 25 days after its birth to triple its weight.