John bought some pens and pencils at book store. if 5 pens and 3 pencils cost $13 while 5 pencils and 3 pens cost $11 instead, f
ind the cost of a pen.
1 answer:
Answer:
$2
Step-by-step explanation:
Let the cost of a pen and a pencil be $x and $y respectively.
5x +3y= 13 -----(1)
5y + 3x= 11
3x +5y= 11 -----(2)
(1) ×5:
25x +15y= 65-----(3)
(2) ×3:
9x +15y= 33 -----(4)
(3) -(4):
25x +15y -(9x +15y)= 65 -33
Expand:
25x +15y -9x -15y= 32
Simplify:
16x= 32
Divide both sides by 16:
x= 32 ÷16
x= 2
Thus, a pen costs $2.
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