the cost of three notebooks and four pencils is $8.50. the cost of five notebooks and eight pencils is $14.50. what is the cost of one pencil

Question

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Answer 1

3n +4p = 8.5

5n + 8p=14.5

 

multiple 1st equation by -2 and add the equations together to solve for n

-6n-8p=-17

5n +8p=14.5

-1n = -2.5

n=2.5

 

and sub 'n' into an equation:

3(2.5) +4p =8.5

7.5 +4p = 8.5

4p = 1

p = .25