Well to find this answer, you would have to know the formula of a line, or also known as slope intercept form-- "y= mx+b"
1) Let's find the slope between the two points! (Use the y1-y2 over x1-x2 slope formula)
y1-y2
-------- = slope formula. Use the points 2,8 and 4,12
x1-x2
12-8 4 2
------ = ---- = ----- = our slope is 2!
4-2 2 1
^---- Here we simplify
2) Now we know our slope is 2! Substitute this into the y=mx+b formula
y=2x+b
3) Take one of the points we used for finding the slope and substitute it into our slope-intercept formula. That way we can solve for "b", our y-intercept.
y=2x+b
8= 2(2)+b MULTIPY
8= 4 +b
-4 -4 SUBTRACT (inverse operations)
----------
4=b SIMPLIFY (our final answer)
4) Now we know our y-intercept! Substitute it into the slope-intercept form to get our line.
y=2x+b
y=2x+4
5) Check your work by taking one of the points from above and substitute again!
y=2x+b
12= 2(4)+4
12= 8+4
12=12
Our equation works!