Question 386751
Definition of supplementary - 2 angles with a sum of 180 degrees.  
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Therefore:

(2P+9)+ (3p-4) = 180

5p + 5 = 180

5p = 175

p = 35
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To find the angle measures, plug in 35.
2p+9 = 2(35) + 9 = 79
3p-4 = 3(35) - 4 = 101
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Check:
101 + 79 = 180 :)