New driver needs help..

[Bulletproof]

Hi, Im going to be a new driver soon and am going to take the written test for my license, I've been studying the book and there is one part that is driving me crazy where I cant picture the question:

"When two vehicles enter an intersection from different highways at the same time, which vehicle must yield the right-of-way"

Now I know the answer is the vehicle on the left, but this is just from memorizing the answer, I can't picture this situation in my mind and I just don't understand the question. I would really appreciate it if someone could explain it to me in detail or even better if someone could do a quick draw up for me in mspaint or some drawing program.