I know the solutions to Y=3x-1 is (1,2) and (2,5) but how do I get those answers? How do I find out those are correct.

Simply  which value you put for x  you will get some answer for y that makes x and y coordinates..

Step-by-step explanation:

Like when  x=0

y=3(0)-1=-1

when x=1

y=3(1)-1

y=3-1

y=2

When x=2

y=3(2)-1

y=6-1

y=5

When x=3

y=3(3)-1

y=8