help pleaase i dont understann

Answer:
The length of x is 12.
Step-by-step explanation:
Here's the required formula to find the missing side of triangle :
[tex]{\longrightarrow{\pmb{\sf{{(a)}^{2} + {(b)}^{2} = {(c)}^{2}}}}}[/tex]
Substituting all the given values in the formula to find the third side of triangle :
[tex]\begin{gathered} \quad{\longrightarrow{\sf{{(a)}^{2} + {(b)}^{2} = {(c)}^{2}}}}\\\\\quad{\longrightarrow{\sf{{(x)}^{2} + {(16)}^{2} = {(20)}^{2}}}}\\\\\quad{\longrightarrow{\sf{{(x)}^{2} + (16 \times 16) = (20 \times 20)}}}\\\\\qquad{\longrightarrow{\sf{{(x)}^{2} + (256) = (400)}}}\\\\\qquad{\longrightarrow{\sf{{(x)}^{2} + 256 = 400}}}\\\\\qquad{\longrightarrow{\sf{{(x)}^{2} = 400 - 256}}}\\\\\qquad{\longrightarrow{\sf{{(x)}^{2} = 144}}}\\\\\quad{\longrightarrow{\sf{x = \sqrt{144}}}}\\\\\quad{\longrightarrow{\sf{\underline{\underline{\purple{x = 12}}}}}} \end{gathered}[/tex]
Hence, the length of x is 12.
[tex]\rule{300}{2.5}[/tex]