Answer:
-12
Step-by-step explanation:
The y-intercept is where x is zero. Since x already equals zero, the y-intercept is -12. For future reference, you can calculate this by putting the coordinates into your equation y=mx+b, so that would look like -12=3(0)+b. Then you get b all by its self by bringing the 3(0) to the other side. (-12)-3(0)=b to get your answer of -12
