How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Speaking of rivers, a man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

I know there are two methods by using three time the same number with a plus(+) operator , you can make sum as 60.

One of them is 20+20+20.

whats the other way ?

What is the Surname of Barbie Doll?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

How many times can you subtract the number two from the number fifty?

Why is the Hole below a Lock?

You need to arrange three 7 and mathematical symbols to form number 1?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()