I don't understand these, please help!

Step-by-step explanation:
2A
x=1 y=3
x=4 y=0
y=mx+b
3=m+b
0=4m+b
3=-3m
m= -1
0=-4+b
b=4
y= -x +4
2B
x=2 y=0
x=0 y= -4
0=2m+b
-4=b
b=-4
0=2m-4
2m=4
m=2
y=2x-4