Can someone help me understand how it simplifies to the second equation​

Answer:Here's what I get.Step-by-step explanation:[tex](f \circ f)(x) = \dfrac{2 }{\dfrac{2 }{x - 7}- 7}[/tex]1. Simplify the denominator[tex]\begin{array}{lrcl}\dfrac{2}{x-7}-7&=&\dfrac{2}{x-7} -\dfrac{49}{7}&\text{Wrote 7 as improper fraction} \\\\ & = &\dfrac{14 - 49(x - 7)}{7(x - 7)} &\text{Put over common denominator} \\\\ &=& \dfrac{2 - 7(x - 7)}{x - 7} &\text{ Removed the common factor (7)}\\\\ & = & \dfrac{2 - 7x + 49}{x-7} &\text{Distributed the 7} \\\\ & = & \dfrac{51-7x}{x-7} &\text{Combined like terms} \\\\\end{array}[/tex]2. Do the division[tex]\begin{array}{lrcl}(f \circ f)(x) & = & \dfrac{2}{\left ( \dfrac{51-7x}{x-7} \right )}& \\\\ & = & 2 \times \dfrac{x - 7}{51 - 7x} &\text{Inverted the fraction and changed divide to multiply} \\\\ (f \circ f)(x)& = & \mathbf{\dfrac{2(x - 7)}{51 - 7x}} &\text{Put over common denominator}\end{array}[/tex]