Plz john and sara each bought the same type of pen and notebook in the school bookstore, which does not charge sales tax. john paid $5.55 for two pens and three notebooks, and sara paid $3.50 for one pen and two notebooks. how much does the school bookstore charge for one notebook? show work

Hey!
Let p = cost of a pen 
Let n = cost of a notebook 

The info in the question leads to two equations: 

1) 2p + 3n = 5.55 
2) p + 2n = 3.50 

Multiply equation 2) by 2 to get the new system of equations 

1a) 2p + 3n = 5.55 
2a) 2p + 4n = 7.00 

Subtract equation 1a) from equation 2a) to get 

n = 1.45 that's the cost of one notebook 

 
To check, you could go on to figure out p, which turns out to be 0.60 . Put in those values of n and p into the original equations to verify.
Hope this helps! ~Nadia~