1.
the closest perfect squares of 12 are 9 and 16,
that is 9<12<16
so


this means,

is 3 point something...
2.
similarly
36<40<49
so


which means

is 6 point something...
3.
the sum of the integers between the square root of 12 and 40 is the sum of 4, 5 and 6, since 4 is the smallest integer after root 12, and 6 the greatest integer to before root of 40.
Answer: 15