Answer:
y = 400x - 1200
Explanation:
considering the linear equation y = mx + c
where y denotes number of items
x denotes item price
we have y = 2000 and x = $8 so we have now
2000 = m(8) + c ...... 1
now we have
y = 400 and x = $4
400 = m(4) + c .....2
from equation 1 and 2 we have
subtracting 2 from 1
1600 = 4m
m = 400
solving for c value
400 = 4m + c
400 = 4*400 + c
c = -1200
y = 400x - 1200