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In a stationary store,pencils have one price and pens have another price.Two pencils and three pens cost 78 cents.However, 3 pencils and 2 pens cost 72 cents . How much does one pencil cost?

Respuesta :

Desidemona

Answer:

12¢

Step-by-step explanation:

Let the unit price of a pencil be x and the unit price of a pen be y.

2x+3y=78¢

3x+2y=72¢

(2x)+3y=78¢

(3x)+2y=72¢

=2x=78¢-3y

=2x/2=78¢/2+3y/2

=x=36¢-1.5y

You then use the equation 3x+2y=72¢.

3(36¢-1.5y)+2y=72¢

=117¢-4.5y+2y=72¢

=117¢-72¢=4.5y-2y

=45¢=2.5y

=45¢/2.5=y

=18¢=y

So a pen costs 18¢.

You then use x=36¢-1.5y

x=36¢-1.5(18¢)

=x=36¢-27¢

=x=12¢

Therefore, a pencil costs 12¢.

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