Answer:
1) Base - 5
2) Base - 1.2
3) Base - 
Step-by-step explanation:
To find : Write the base number for each expression ?
Solution :
Base number is defined as the number written in exponent form 
which tells you to multiply a by itself, so a is the base of power n.
1) 
In number
the base is 5 as the power is 12.
2) 
In number
the base is 1.2 as the power is 2.
3) 
In number
the base is
as the power is 4.