c. -5
Explanation
given
[tex]7-\sqrt{4-x}=4[/tex]
Step 1
a) subtract 7 in both sides
[tex]\begin{gathered} 7-\sqrt{4-x}=4 \\ 7-\sqrt{4-x}\text{ -7}=4-7 \\ -\sqrt{4-x}=-3 \end{gathered}[/tex]
b) divide both sides by -1
[tex]\begin{gathered} -\sqrt{4-x}=-3 \\ \frac{-\sqrt{4-x}}{-1}=\frac{-3}{-1} \\ \sqrt{4-x}=3 \end{gathered}[/tex]
c) now, toeliminate the root, power two sides to 2
[tex]\begin{gathered} \sqrt{4-x}=3 \\ (\sqrt{4-x})^2=3^2 \\ 4-x=9 \end{gathered}[/tex]
d) subtract 4 in both sides
[tex]\begin{gathered} 4-x=9 \\ 4-x-4=9-4 \\ -x=5 \\ x=-5 \end{gathered}[/tex]
therefore, the answer is
c. -5
I hope this helps you
