we use the pythagorean theorem
1)
[tex]\begin{gathered} c^2=a^2+b^2 \\ c^2=15^2+20^2 \end{gathered}[/tex]
and
[tex]\begin{gathered} c^2=225+400 \\ c^2=625 \\ c=\sqrt[]{625}=25\text{ in} \end{gathered}[/tex]
2)
[tex]5^2+b^2=13^2[/tex]
and
[tex]\begin{gathered} 25+b^2=169 \\ 25+b^2-25=169-25 \\ b^2=144 \\ b=\sqrt[]{144}=12\text{ in} \end{gathered}[/tex]
c)
[tex]28^2+b^2=35^2[/tex]
and
[tex]\begin{gathered} 784+b^2=1225 \\ 784+b^2-784=1225-784 \\ b^2=441 \\ b=\sqrt[]{441}=21\text{ in} \end{gathered}[/tex]
