A spider ate 25% more bugs this month than last month.The spider ate 8 bugs last month. How many bugs did the spider eat this month?

To increase by a percentage, multiply by the 1+(the percentage/100). i.e. in this case to find 25% we'd multiply by 0.25, so to increase by 25% we basically find 125% of it, which involves multiplying by 1.25.

8*1.25 is 10, so the spider ate 10 bugs this month.