Essential University Physics: Volume 1 (3rd Edition)

$F=500N$
As torque about pivot is zero $\implies mg\times x-F\times 22=0$ This can be rearranged as: $F=\frac{mgx}{22}$ We plug in the known values to obtain: $F=\frac{55\times 9.8\times 20.4}{22}$ $F=500N$