<h2>
Answer:</h2>
1)
         3 , -10
2)
           10x + y
3)
             2x-3y
<h2>
Step-by-step explanation:</h2>
Ques 1)
We are given an algebraic expression as:
                
The following expression has three terms: 

and the constant term is the term in which the variable is of exponent 0.
Hence, here we have the constant term as: 
Ques 2)
We are given a expression in terms of x and y by:

when on simplifying this expression we have:

Ques 3)
The expression is given by:

On using the distributive property i.e. 

we have:
