we know that
In an Arithmetic Sequence the difference between one term and the next is a constant
This problem is an Arithmetic Sequence
where
the first term is [tex] 23 [/tex]
and
the common difference is [tex] -2 [/tex]
In general we can write an Arithmetic Sequence as a rule
[tex] an=a1+d*(n-1) [/tex]
where
a1 is the first term
d is the common difference
so
[tex] a1=23\\\\ d=-2 [/tex]
Find the term a7
[tex] an=a1+d*(n-1)\\ \\ a7=23+(-2)*[7-1]\\ \\\\ a7=23-12\\ \\\\ a7=11 [/tex]
therefore
the answer is
[tex] 11\ tiles [/tex]
