1 file and 1 notebook cost $10. 1 file and 1 pen cost $6. Each notebook costs thrice as much as a pen. How much does 1 file cost?
2 Answers
A files costs
Explanation:
Let the following variables apply (with all values in dollars):
#color(blue)f# : cost of a file#color(green)n# : cost of notebook#color(magenta)p# : cost of a pen
We are told
[1]
[2]
[3]
From [3] we know we can substitute
[4]
Subtracting [2] from [4]
[5]
which implies
[6]
From [6] we know we can substitute
[7]
and, after subtracting
[8]
Explanation:
Let the cost of pen be
From A & B,
Equating C & D,
From B,