What do the symbols in parenthesis indicate?
cacl2(aq) + 2agno3(aq)) → ca(no3)2(aq) + 2agcl(s)

Aq means it's soluble in H2O by default

s means it's solid, not soluble.

It indicates physical state of that compound.
aq is for aqueos.
s is for solid
l is for liquid and
g is for gaseous state.

Hope this helps you.

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na