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