Which of the following sets of forces acting simultaneously on a particle keep it in equilibrium                               

gf – greatest force; sgf – second gf

$3,5,10$

$\text{gf}-10,\text{sgf}-5$

$\Rightarrow 10-5=5$

$5>3$

$4,7,12$

$\text{gf}-12,\text{sgf}-7$                        

$\Rightarrow 12-7=5$

$5>4$

$2,6,\text{}5$

$\text{gf}-6,\text{sgf}-5$

$\Rightarrow 6-5=1$                              

$5>4$

$5,\text{}8,1$

$\text{gf}-8,\text{sgf}-5$

$\Rightarrow 8-5=3$

$3>1$

Their difference must be less than the third side in triangle. Then there will be equilibrium.

The set of forces can possible to make triangle, those can keep the particle in equilibrium.