  We explain how the invariant subspace method can be extended to a scalar and
coupled system of time-space fractional partial differential equations. The
effectiveness and applicability of the method have been illustrated through
time-space (i) fractional diffusion-convection equation, (ii) fractional
reaction-diffusion equation, (iii) fractional diffusion equation with source
term, (iv) two-coupled system of the fractional diffusion equation, (v)
two-coupled system of fractional stationary transonic plane-parallel gas flow
equation and (vi) three-coupled system of fractional Hirota-Satsuma KdV
equation. Also, we explicitly presented how to derive more than one exact
solution of the equations as mentioned above using the invariant subspace
method.
