So, you need to know that the slope stays where it is, and that the 6 is not part of the final answer, so get rid of it.
y=2x+b
Now, submit x in for x, and y in for y.
3=2(1)+b
3=2+b
1=b
Put this in for the equation missing the b,
y=2x+1
Now check it; if you put 1 in for x, does y=3?
The answer i pretty sure would be 3x
0.1442
0.1714
0.05487
0.2075
x = 5.
I attached an image of my work!
Step 1: Subtract 8 from both sides
4x = 20
Step 2: Divide each side by 4
x = 5
The y intercept (b) = 4 and the slope (m) is 12
y = mx + b so its:-
y = 12x + 4