Can someone help me with these 2 questions?

http://gyazo.com/582fd4017744e770d813f69cb76579c6

Question

Can someone help me with these 2 questions?

http://gyazo.com/582fd4017744e770d813f69cb76579c6

texaschic101 · Answer

9. 15a + 5k = 390
(1) 15(9) + 5(51) = 390
     135 + 255 = 390
      390 = 390 (this is possible)
(2) 15(17) + 5(27) = 390
     255 + 135 = 390 (this is possible)
(3) 15(21) + 5(15) = 390
     315 + 75 = 390
     390 = 390 (this is possible)
(4) 15(23) + 15(0) = 390
      345 + 0 = 390
       345 = 390 (NOT POSSIBLE) < -- your answer

10. Horizontal line passes through (-5,9)
      Horizontal lines : their equations are in the form of : y = a constant
Therefore, your answer is : y = 9