Answer:
[tex]\text{D.}\quad d=\dfrac{206-8(10)}{7}[/tex]
Step-by-step explanation:
The total length of the space between rungs is the overall length less the width of 8 rungs, so is 206 -8(10). That space is divided into 7 equal parts, as shown by the equation in choice D.
_____
Choice A looks similar, but is not. In that equation, only the term 8(10) is divided by 7. You want the difference to be divided by 7, so must have a grouping symbol of some kind. Choice D uses the division bar to group the terms of the numerator. Parentheses would work, too, as in ...
d = (206 -8(10))÷7
but without them, the equation is incorrect.
