(-)(-) = +
(-)(+) = -
that's the rule...hope that helps:D
If the two angles are a linear pair, this means that they are supplementary and both add up to 180 degrees. So set up the equation:
3x + 7 + 9x + 17 = 180
--> 3x + 9x + 17 + 7 = 180
--> 12x + 24 = 180
-->12x = 180 - 24 = 156
-->156/12 = 13, so x = 13
Plug in the x value:
3(13) + 7 = 46 degrees
9(13) + 17 = 134 degrees
To check your work, 134 + 46 = 180.
Your answer is A.
3(13) + 7 = 46
9(13) + 17 = 134
Which concludes that your answer is A!