In the given figure the number of block are increase by 2
So, The expression show an series of Airthmetic sequence where nth term is express as:

So, the rate of change in teh system is 2
Slope =2
The expresion in the y = mx +b
Here we get m = 2
So,
equation will be :

where x respresnt the number of pattern and y represnt the number of blocks.
Answer : Expression : y = 2(x-1) + 1