Answer:
Clara can feed 10 friend
I may be wrong, but I tried :P

x=8
16-8=8

Use a calculator to find the square root of 8.
Step-by-step explanation:
let's assume one month is 30 days you would multiply 10 by 30.

which would be 300 hours in 1 month
now if one month is 31 days you would simply multiply 10 by 31.

which would be 310 hours