To better illustrate the problem, we will try to enumerate the different types of reaction.
1. Combustion - reaction with oxygen to form Carbon dioxide and water
2. Synthesis - two or more simple compounds joined together to form a more complicated compound.
A + B ---> AB
3. Decomposition- opposite of synthesis reaction.
AB -----> A + B
4. Single - one element displace/replace an element in a compound
AB + C ----> AC
5. double - it is a switching places of ions during reaction.
AB + CD ----> AD + CB
6. Acid base - a type of double replacement wherein H+ and OH- is involved. Salts are formed in this type of reaction.
HCl + NaOH -----> NaCL + H2O
By inspection we can see that:
ZnBr2 (aq) + 2AgNO3 (aq) -->Zn(NO3)2 (aq) + 2AgBr (s)
is a double displacement reaction. We can also call this as precipitation reaction since AgBr precipitates in the reaction (it is denoted by a letter (s) in the chemical reaction).
KBr (aq) + AgNo3 (aq) --> AgBr (s) + KNO3
similarly, this is also a double replacement reaction/precipitation reaction.
hope this helps :)