Which number should replace the question mark?

Can you solve this picture maths equation?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

Sally lives in a place where six months of the year is mild summer and the temperature drops significantly the other six months. She owns a lake where there is a small island. She wants to build a house on the island and needs to get materials there. She doesn’t have a boat, plane, or anything to transport them to the island. How does Sally solve this problem?

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

What goes through cities and fields, but never moves?

What is the coolest letter in the alphabet?

Find the number of squares in the below picture