The San Andreas Fault separates the Pacific plate from the North American plate. The Pacific plate moves northward relative to the North-American plate at a rate of 5.5
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Los Angeles rests on the Pacific plate whereas San Francisco is on the North American plate. Currently the distance between Los Angeles and San Francisco is about 520 km.

How long will it take Los Angeles to be next to San Francisco? answer in years

California is a state that lies on two separate plates, with part of it being on the North American plate and part of it being on the Juan de Fuca plate (not the Pacific plate as it is stated), and these two plates have a transform plate boundary, meaning that they slide past each other. Over the course of millions of years, this will result in places that are now far away to be right next to each other or to switch their locations relative to each other.

San Francisco and Los Angeles are good for example because they lie on opposite plates and move toward each other. With an annual rate of movement of 5.5 cm and a distance of 520 km between them, we can easily discover how much time will be needed for them to come next to each other. We first need to convert the km into cm:

1 km = 100,000 cm

520 x 100,000 = 52,000,000 cm

Now we need to divide the cm between them with the rate of movement:

52,000,000 / 5.5 = 9,454,545

We get a result of 9,454,545, meaning that that is the number of years needed for these two cities to come next to each other if the current rate and direction of movement continues in the future as well.