Given that OB = AB, OAB is an isosceles triangle. The angles opposite the equal sides are equal, so OAB = AOB.

Here's the solution for the bearing problem:

a) Calculate the bearing of B from A

Step 1: Find the angles in $\triangle OAB$.
Given that $OB = AB$, $\triangle OAB$ is an isosceles triangle. The angles opposite the equal sides are equal, so $\angle OAB = \angle AOB$.
The sum of angles in a triangle is $180^\circ$. We are given $\angle ABO = 40^\circ$.

$$\angle OAB + \angle AOB + \angle ABO = 180^\circ$$

Since $\angle OAB = \angle AOB$, let $x = \angle OAB$.

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