40 - 4 = 36
average = 36/9 = 4
answer
average number of members who joined the math club is 4 per month
Answer:

Step-by-step explanation:
How do we find the line that's perpendicular to another?
We find the negative reciprocal. So for example if our slope is 2, the negative reciprocal would be
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The 2 angles at a vertex are supplementary (one interior and one exterior) the exterior angle is = the the sum of the 2 remote interior angles..