Answer:
There are 156 concrete blocks available to make a wall.
The bottom three rows will all have the same number of blocks.
The next six rows will each have two blocks fewer than the row below it.
Let there be x blocks in the first 3 rows.
As per the situation, the expression becomes:
[tex]3x+x-2+x-4+x-6+x-8+x-10+x-12=156[/tex]
=> [tex]9x-42=156[/tex]
=> [tex]9x=156+42=198[/tex]
=> [tex]x=\frac{198}{9}[/tex]
x =22
So, there are 22 blocks in the first 3 rows.
And in each successive rows we have : 20,18,16,14,12 and 10
If we total all, we get 156.
[tex](22\times3)+20+18+16+14+12+10[/tex]
[tex]66+20+18+16+14+12+10=156[/tex]
