Hey there!
In order to do that, you take both of the x values and plug them back in to see if you got the desired y value. If you do, it's correct.
For example:
If you had the equation:
y = 2x + 5
and had the points (5,15) and (3,1)
We would check the first coordinates by plugging in the x value:
y = 2(5) + 5
y = 15
Since 15 is our y value, we're correct.
For our next, we can do the same thing, and plug in the x value:
y = 2(3) + 5
y = 6 + 5
y = 11
Since we don't have our desired value, we know we're wrong.
Hope this helps!