An ant is on a picnic table. it travels 30 cm eastward, then 25 cm northward and finally 15 cm westward. What?

See its very simple

ant moves 30cm to east and 15 cm to west it means that it is 15 cm to the east of the original point

now it moved 25 cm to the north so take 25 cm as perpendicular and 15 cm as base So tan@=25/15

so @=tan^-1(25/15) which is approximately = 59deg to north of east

This type of question is really easy if you just remember that you can add vector components to come up with a new resultant vector. So, since east and west are in opposite directions, you figure that the total east-west displacement is 30-15=15 cm eastward.

The northward direction is just 25 cm. Since you know the distance north and east, look at your choices to see that the question wants an answer in the form of a bearing North of East or North of West. Looking at the resultant vector components (15,25) you can see that they are both positive so it will lie in the first quadrant. So, you only need to break out your handy TANGENT function to figure out the angle. Since you know that only east and north are involved, the answer must be:

tan^-1(25/15) = 59° N of E