To help us determine the direction, let's make an illustration of the problem.
1. 25 km 30°SW
2. 30 km N to the second oasis
To determine the value of x, we can use sine function.

where the opposite side of the angle is 30 - x km while the hypotenuse is 25 km. Let's plug this in to the function above.

Using Pythagorean Theorem, let's solve for the value of y.
![\begin{gathered} y=\sqrt[]{(25km)^2-(30km-xkm)^2} \\ y=\sqrt[]{25^2-12.5^2} \\ y=\sqrt[]{625-156.25} \\ y=\sqrt[]{468.75} \\ y=21.6506km \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/vdqjj7kqntjwhzi0fl3ritybhpd28jxo0l.png)
To get the angle formed by x = 17.5 km and y = 21.6506km, let's use the tangent function.

This means the direction of the oasis is 39° North of West or 51° West of North. The answer is found in Option D.