Question 1081575
(1) 5N+P = 7
(2) 2N+2P = 4

(1) ==>  P = 7-5N
Subs into (2):

   2N + 2(7-5N) = 4
   2N + 14 - 10N = 4
    -8N = -10  
       {{{highlight( N = 1.25) }}}  

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Check:   N=1.25 —> P=0.75
         (1) 5(1.25) + 0.75 = 6.25 +0.75 = 7  (ok)
         (2) 2(1.25) + 2(0.75) = 2.5 + 1.5 = 4 (ok)