Answer:
Let x and y be the two positive integers the Christopher is thinking.
x is equal to 7
and y =20
Cost of the current plan: $175
Number of devices: x
Cost of the new plan: $94+($4.50/device)x
Cost of the new plan is less than the current plan:
$94+($4.50/device)x<$175
Solving for x:
$94+($4.50/device)x-$94<$175-$94
($4.50/device)x<$81
(device/$4.50)($4.50/device)x<(device/$4.50)($81)
x<18 devices
Please, see the attached file.
Thanks.
The answer to the question is 4x - y ≥ 4