The cost of one pack of ballpoint pens is $3 and the cost of one pack of gel pens is $7.
Let
x -----> the cost of one pack of ballpoint pens
y -----> the cost of one pack of gel pens
we know that
60x+25y=355 -----> equation A
120x+30y=570 -----> equation B
Solve the system of equations by graphing
The solution is the point (3,7)
see the attached figure
therefore
The cost of one pack of ballpoint pens is $3
The cost of one pack of gel pens is $7
Thus, this could be the answer.
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