A line has a slope of 2. It passes through the point (1,2) and (3,y). What is the value of y ?

Please help.
Is there like a specific difference I'm suppose to find?
I'm super confused.

x grows by 2

the slope is 2, so y grows by 4.

so, y=2+4=6

or, more formally,

(y-2)/(3-1) = 2