A child is making a 5-level pyramid by stacking some blocks. In the first row, he has 9 blocks. For the next rows, he has 2 less than the blocks he has from its bottom row. How many blocks did he use in all?
On the second row, he used 9 - 2 = 
<gadget id="calculator">9-2</gadget>
<output>7</output>
7 blocks.
On the third row, he used 7 - 2 = 
<gadget id="calculator">7-2</gadget>
<output>5</output>
5 blocks.
On the fourth row, he used 5 - 2 = 
<gadget id="calculator">5-2</gadget>
<output>3</output>
3 blocks.
On the fifth row, he used 3 - 2 = 
<gadget id="calculator">3-2</gadget>
<output>1</output>
1 block.
Therefore, he used a total of 9 + 7 + 5 + 3 + 1 = 
<gadget id="calculator">9+7+5+3+1</gadget>
<output>25</output>
25 blocks.

<result>25</result>