The general term in the binomial expansion,
Tr+1=Cr22(xm)22−rx−2r
⇒Tr+1=Cr22xm(22−r)−2r
For the coefficient of x
22m−mr−2r=1
⇒22m−1=r(m+2)
⇒r=m+222m−1
⇒r=m+222m+44−45
r=22−m+23.3.5⇒22−r=m+23⋅3⋅5
Since, Cr22=C22−r22
So possible values of m=1,3,7,13,43, but C322=1540⇒22−r=3⇒m=13