Greetings :)
To find slope of two points we will need to use this equation: 
( 6 , -12 ) ( 15 , -3 )
Now let's replace the equation with the numbers. (it will be a fraction).
= 
The equation equals 9 over 9, which also equals 1.
The slope of the line is 1.
Answer:
y = x + 6.
Step-by-step explanation:
y = mx + c where m = the slope of the line and c is the y-intercept.
So here m = 4/4 = 1 and c = 6, so it's:
y = 1x + 6.