Please help me and explain to me!

Step-by-step explanation:
use phytagoras theorem to find the length of broken post
[tex] \sqrt{ {7}^{2} } + {10}^{2} [/tex]
[tex] \sqrt{49 + 100} [/tex]
[tex] \sqrt{149} [/tex]
[tex] = 12.2[/tex]
add the broken post with the standing
= 7 + 12.2
=19.2