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lisabon 2012 [21]
3 years ago
7

ABC bookstore sells one customer 12 used books and 4 new books for $120.

Mathematics
2 answers:
Ede4ka [16]3 years ago
7 0

Answer:

One used book cost 5$ and a new book cost 15$

Step-by-step explanation:

\left \{ {{12u + 4n = 120} \atop {14u + 2n = 100}} \right. \\

lets multiply the second equation ×(-2)

×\left \{ {{12u + 4n = 120} \atop {(-2)*(14u + 2n = 100)}} \right. \\\\\left \{ {{12u + 4n = 120} \atop {-28u - 4n = -200}} \right. \\\\\\\left \ {{-16u + 0n = -80} \\,\\\left \ {{16u = 80}\\,\left \ {{u = 5} \\\\

if u = 5 then from equation 1

12*u + 4n = 120, 60 +4n = 120, 4n=120-60, n=60/4, n=15

Reptile [31]3 years ago
5 0

Answer: u=$5, n=$15 APEX

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