There are 10 pencils in a pencil box. We should give them to 10 children. Each child gets one. How can we get one left in the box?

There are 10 pencils in a pencil box. We should give them to 10 children. Each child gets one. How can we get one left in the box?

It's so hard. It's so hard!
It's OK to give the tenth child the box

Old lady Wang goes to the market to sell eggs. The first person buys half and one of the eggs in the basket, and the second person buys half and one of the remaining eggs. At this time, there is still one egg left in the basket. How can old lady Wang sell all the eggs______ I'll have an egg

The second person bought: (1 + 1) × 2 = 4 (pieces), the total number of eggs: (4 + 1) × 2 = 10 (pieces), the number of eggs sold: 10-1 = 9 (pieces); answer: Mrs. Wang sold a total of 9 eggs

There are 14 poplar trees planted on the roadside, and a willow tree is planted between every two trees. How many willows should be planted?;;
The required formula can only be addition and subtraction
Thank you very much
And it's adding and subtracting. It's adding and subtracting.

14-1=13

First grade math, online, etc
4-1=3
4-3=1
5-2=3
5-3=2
Through the above, what conclusions are drawn
Please be more detailed

I am a teacher, I hope my answer can give you some help!
It's wrong to go upstairs!
You can see that subtraction from the subtracted equals difference,
The subtraction of the difference from the subtracted equals the subtraction