what is the nature of mixture when 10gram ice is mixed at -20degree centigrade us mixed with 50gram at 120 degree centigrade?

Well, heat the ice and melt it first.

Heat1=10*cice*(0+20)+10Hf now it is at zero C

then find the heat released by the steam to get to 100C
Heat2=50*Csteam(100-120)+50Hv
notice this is negative heat gained.(Hv is negative).

Now, you have water at 100C and OC.

Sum of heats is zero.
Heat1+Heat2+10*Cw*(Tf-0)+50cw(Tf-100)=0
solve for Tf, Remember, HEAT2 IS NEGATIVE