  Observationally, for neutron star low-mass X-ray binaries, so far, the
correlation between the radio luminosity $L_{\rm R}$ and the X-ray luminosity
$L_{\rm X}$, i.e., $L_{\rm R}\propto L_{\rm X}^{\beta}$, has been reasonably
well-established only in three sources 4U 1728-34, Aql X-1 and EXO 1745-248 in
their hard state. The slope $\beta$ of the radio/X-ray correlation of the three
sources is different, i.e., $\beta \sim 1.4$ for 4U 1728-34, $\beta \sim 0.4$
for Aql X-1, and $\beta \sim 1.6$ for EXO 1745-248. In this paper, for the
first time we explain the different radio/X-ray correlation of 4U 1728-34, Aql
X-1 and EXO 1745-248 with the coupled advection-dominated accretion (ADAF)-jet
model respectively. We calculate the emergent spectrum of the ADAF-jet model
for $L_{\rm X}$ and $L_{\rm R}$ at different $\dot m$ ($\dot m=\dot M/\dot
M_{\rm Edd}$), adjusting $\eta$ ($\eta \equiv \dot M_{\rm jet}/\dot M$,
describing the fraction of the accreted matter in the ADAF transfered
vertically forming the jet) to fit the observed radio/X-ray correlations. Then
we derive a fitting formula of $\eta$ as a function of $\dot m$ for 4U 1728-34,
Aql X-1 and EXO 1745-248 respectively. If the relation between $\eta$ and $\dot
m$ can be extrapolated down to a lower value of $\dot m$, we find that in a
wide range of $\dot m$, the value of $\eta$ in Aql X-1 is greater than that of
in 4U 1728-34 and EXO 1745-248, implying that Aql X-1 may have a relatively
stronger large-scale magnetic field, which is supported by the discovery of the
coherent millisecond X-ray pulsation in Aql X-1.
