Answer:
-3/2 or -2.5
Step-by-step explanation:
Use the y=mx+b formula
Subsitute given values...
y=-1/7x+b
use the point (-21,1/2) to substitute values for x and y
1/2=-1/7(-21)+b
solve
1/2=3+b
subtract both sides by 3
-3/2 = b
Therefore the answer is -3/2
