It looks like you have a set of questions from a math test. Let's break them down one by one:

a) Simplify the expression:
$2x^2 + xy + y^2 - x^2 + 6y^2 + 4y + 8xy$

We will group like terms and simplify.

b) Expand and simplify the expression:
$(x + 3)(x - 4)(2x + 7)$

We'll expand this expression by multiplying each term systematically.

c) Evaluate the expression:
$2x^3 + 5x^2 - 31x - 84$ using $x = 4$

We will substitute $x = 4$ into the expression and calculate the value.

d) For the table:
We need to determine whether each item is an equation or an expression.

Let's start with part a:
Simplify the expression $2x^2 + xy + y^2 - x^2 + 6y^2 + 4y + 8xy$

We can combine like terms:

• $2x^2 - x^2 = x^2$
• $xy + 8xy = 9xy$
• $y^2 + 6y^2 = 7y^2$
• The remaining term is $4y$

So, the simplified expression is:
$x^2 + 9xy + 7y^2 + 4y$

Would you like me to continue solving the next parts, or do you have any questions on this?