Answer
$2n-1$
Work Step by Step
Notice that each time the figure increases by two squares.
This means that the relationship is linear with a rate of change (slope) of $2$.
Thus, the initial expression that will represent the number of squares is $2n$ where $n$ is the $n$th figure..
Also notice there is one square initially.
This means that if $n=1$, the number of squares is $1$.
Thus, the expression would be $2n-1$.
