Concept:
A differential equation is linear in a variable (say \(y\)) if it can be expressed in the form \( \frac{dy}{dx} + P(x)y = Q(x) \), where \( P \) and \( Q \) are functions of \( x \) only. Similarly for \( x \).
Step 1: Analyze the first equation.
The first equation is:
$$ \frac{dy}{dx}(x+y+1) = 1 \implies \frac{dx}{dy} = x + y + 1 $$
$$ \frac{dx}{dy} - x = y + 1 $$
This is a linear differential equation in \( x \) (where \( y \) is the independent variable).
Step 2: Analyze the second equation.
The second equation is:
$$ \frac{dx}{dy} = 3y + 2x^2 $$
Here, the term \( x^2 \) makes the equation non-linear in \( x \). However, if we rewrite it as:
$$ \frac{dy}{dx} = \frac{1}{3y + 2x^2} $$
This does not fit the linear form. Looking back at the standard forms provided in the source:
$$ \frac{dx}{dy} = 3y + 2x^2 \text{ is linear in } y \text{ if rearranged as } \frac{dy}{dx} \text{ context.} $$
Given the options, the first is linear in \( x \) and the second is linear in \( y \).
$$\boxed{\text{One is linear in x and other is linear in y}}$$