4)
In the case of a square, its diagonals are equal and bisect each other, meeting at 90°.
In our case, using a diagram,
Therefore,
[tex]\begin{gathered} a+2b=90 \\ and \\ 2a-b=90 \end{gathered}[/tex]
Solving the system of equations for a and b,
[tex]\begin{gathered} \Rightarrow a=90-2b \\ \Rightarrow2(90-2b)-b=90 \\ \Rightarrow5b=90 \\ \Rightarrow b=18 \end{gathered}[/tex]
Finding a,
[tex]\begin{gathered} b=18 \\ \Rightarrow a=90-2*18=90-36=54 \end{gathered}[/tex]
The answers are a=54, b=18
