A university bookstore recently sold a wirebound graph-paper notebook for $2.55, and a college-ruled notebook for $3.22. At the start of spring semester, a combination of 50 of these notebooks were sold for a total of $157.65. How many of each type were sold?

Question

anonymous · Answer

Doyou know how to solve systems of linear equations?

anonymous · Answer

using simultaneous eq's

let x = graph book
let y = ruled book

since 50 were sold in total---> x + y = 50

and since the total earnings were 157.65 ---> 2.55x +3.22y = 157.65

multiply the top eq. by 3.22 so that the x terms can be eliminated...

therefore you get : 3.22x + 3.22y = 161
                        -  2.55x + 3.22y = 157.65

after subtraction you get 0.67x = 3.35

therefore x = 5

substitute the value back into original eq : x + y = 50

so y = 45