Solution:

3rd.

In all the structure, we can find 2 rectangles are found except one i.e 3rd.

Solution:

It can be done in image below.

Solution:

As shown below, we can make equation as 6 = 6 = 6.

Solution:

We just added four matchsticks as shown in below picture.

Solution:

Solution is shown below,

Solution:

solution solved as below.

Solution:

35

Explanation
4 : 1/2 X 1/2 matchsticks squares
17: 1X1 matchsticks squares
9 : 2X2 matchsticks squares
4 : 3X3 matchsticks squares
1 : 4X4 matchsticks squares
================
35

Solution:

811105 is the highest number that can be formed moving two matchsticks.

If your answer was 511108, you're almost right. All you have to do is look at that upside down. See the first picture and then the second.

Solution:

In the picture you can see which matchsticks we have moved.

Solution:

We believe you know that square is also a rectangle.