ANSWER
<em>alternate interior angles theorem</em>
EXPLANATION
According to the alternate interior angles theorem, when two parallel lines are are intercepted by a straight line (transversal) the angles in the interior corners of a Z-shape pattern are congruent.
From the above diagram line r is parallel to line s, therefore
and
because they are alternate interior angles.
See attachment for how to spot alternate interior angles.
The current rate is simply equal to $175 per month, let us call this as rate A:
A = 175
The new rate is $94 plus $4.50 per devices, let us call this as rate B:
B = 94 + 4.50 x
where x is the number of devices connected to the network
The inequality equation for us to find x which the new plan is less than current plan is:
94 + 4.50 x < 175
Solving for x:
4.50 x < 81
x < 18
So the number of devices must be less than 18.
- From the graph, we can actually see that the new rate intersects the current rate at number of devices equal to 18. So it should really be below 18 devices.
