Answer
Equation is $15=10x+7.5$
So, $x=0.75$ ft
Distance between each poster should be 0.75 ft and the spaces at the left and right of the group of posters should be 2.25 ft.
Work Step by Step
First, draw a visual diagram of the problem as done below.
Looking at the diagram, we can see that the length of the posters, spaces on the left and right of group of posters, and the distance between each poster, should all equal to $15$ ft.
We can label the distance between each poster as $x$. This means that the spaces at the left and right of the posters are both $3x$.
So, since everything should add up to $15$, we can use this information to form an equation.
$15=(3x+3x)+(1.5 \times 5)+(4x)$
$15=10x+7.5$
Subtract 7.5 from each side of the equation.
$15-7.5=10x$
$7.5=10x$
Divide each side by 10 to find the value of $x$.
$x=\frac{7.5}{10}$
$x=0.75$ ft
This means the distance between each poster should be 0.75 ft and the spaces at the left and right of the group of posters should be 2.25 ft.
