square root both sides and don't forget to get the positive and negative roots
x=+/-[tex] \sqrt{160} [/tex]
[tex] \sqrt{160} [/tex]=[tex] \sqrt{16} [/tex] times [tex] \sqrt{10} [/tex]
[tex] \sqrt{16} [/tex]=+/-4
answer is
+/-4[tex] \sqrt{10} [/tex]
answer is b