Subscript[[Alpha], 1]={1.50,1.75,1.90,1.95}; c1={0.670,0.860,0.950,0.970}; c2={0.440,0.570,0.630,0.650}; c3={0.400,0.510,0.570,0.580}; c4={0.380,0.490,0.540,0.560}; g1=ListLinePlot[{c1,c2,c3,c4},Frame->True, FrameLabel->{Style["!(*SubscriptBox[([Alpha]), (1)])", Medium, Bold, Black], Style["[Rho]", Bold, Black,10]}, FrameStyle->{Directive[Bold,Black,12],Directive[Bold,Black,12]}, PlotLegends->Placed[{"!(*SubscriptBox[([Alpha]), (2)])=2", "!(*SubscriptBox[([Alpha]), (2)])=4", "!(*SubscriptBox[([Alpha]), (2)])=6", "!(*SubscriptBox[([Alpha]), (2)])=8"}, {0.2, 0.6}], PlotTheme -> "Monochrome", PlotLabel->Style["(a):Utilization Factor", Black,Bold,10]](*You lost a square bracket in the right had for ListLinePlot *)
My problem is the values of $\alpha_1$ are not shown on the x-axis. How can I get these values on the x-axis?
Edit
[I am adding a major edit of the OP's code dump so readers can see what the problem is -- m_goldberg]
Subscript[α, 1] = {1.50, 1.75, 1.90, 1.95};
c1 = {0.670, 0.860, 0.950, 0.970};
c2 = {0.440, 0.570, 0.630, 0.650};
c3 = {0.400, 0.510, 0.570, 0.580};
c4 = {0.380, 0.490, 0.540, 0.560};
ListLinePlot[{c1, c2, c3, c4},
Frame -> True,
FrameLabel ->
{Style[HoldForm[Subscript[α, 1]], Medium, Bold, Black],
Style["ρ", Bold, Black, 10]},
FrameStyle -> {Directive[Bold, Black, 12], Directive[Bold, Black, 12]},
PlotLegends ->
Placed[HoldForm[Subscript[α, 2] = #] & /@ {2, 4, 6, 8}, {0.8, 0.22}],
PlotTheme -> "Monochrome",
PlotLabel -> Style["(a):Utilization Factor", Black, Bold, 10]]
DataRange -> MinMax[Subscript[α, 1]]
$\endgroup$