First overtone of open organ pipe is given as
[tex]f_{1o} = \frac{v}{L_1 + 2e}[/tex]
first overtone of closed organ pipe is given as
[tex]f_{1c} = \frac{3v}{4(L_2 + e)}[/tex]
now they are in unison so we will have
[tex]\frac{v}{L_1 + 2e} = \frac{3v}{4(L_2 + e)}[/tex]
[tex]\frac{1}{30 + 2e} = \frac{3}{4(23 + e)}[/tex]
[tex]90 + 6e = 92 + 4e [/tex]
[tex]e = 1 cm[/tex]
so end correction of both pipes is e = 1 cm