Calculate (in a simplified fraction) the probability of choosing a green marble. Solve for y in the following diagram: Consider the diagram alongside. Write down (with reason) the value of x:

Number of green marbles = 4
Total number of marbles = 40

Divide both the numerator and the denominator by their greatest common divisor, which is 4.

The probability of choosing a green marble is: $\boxed{\frac{1}{10}}$

The angles $2y$ and $y$ are adjacent angles on a straight line. Angles on a straight line sum to $180^\circ$.

The value of $y$ is: $\boxed{60^\circ}$

The angles $75^\circ$ and $x$ are vertically opposite angles.

Vertically opposite angles are equal.
Therefore, $x = 75^\circ$.
The value of $x$ is: $\boxed{75^\circ}$ (Reason: Vertically opposite angles are equal)