Question

En la misma papelería, a Julián le cobraron $40 por 4 lápices y 8 plumas, mientras que a Estefanía le cobraron $25 por 6 lápices y 2 plumas. ¿Cuántos pesos costó cada pluma?

Answer 1

The cost of a pen is $3.5 while the cost of a pencil is $7

Simultaneous equation

Let the price of pen  be x

Let the price of pencil be y

If Julian was charged $40 for 4 pencils and 8 pens, then;

4y + 8x = 40

y + 2x = 10

y = 10 - 2x .............. 1

Similarly, if Estefania was charged $25 for 6 pencils and 2 pens, then;

6y + 2x = 25

Substitute 1 into 2 to have:

6(10-2x)+ 2x = 25

60 - 12x + 2x = 25

60-10x = 25

10x = 35

x = 3.5

Since y = 10 - 2x

y = 10 - 7

y = 3

Hence the cost of a pen is $3.5 while the cost of a pencil is $7

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