Answer:
pencils amount = 9 pens amount= 9
Step-by-step explanation:
We start this problem forming two linear equations system.
3*X+7*Y=90
Where X is the amount of pencils and Y is the amount of pens
The second equation is given by the statement, the amount of pencils is equal to the amount of pens, so the second equation is:
X=Y
Merging both equations we have:
3*X+7*X=90
Solving for X we have:
10*X=90
X=9
X=Y=9
