Question

When three pens and four erasers were purchased,the cost was $21.25. When two pens and two erasers were purchased the cost was $12.50.What was the price of a pen and an erasers.

Answer 1

Let cost of pen= x
Let cost of eraser=y

Given: 3x+4y=21.25
3x=21.25-4y
x=(21.25-4y)/3

Now, 2x+2y=12.50
Putting value of x from previous equation to this equation
2(21.5-4y)/3+2y=12.50
(43-8y)/3+2y=12.50
(43-2y)/3=12.50
43-2y=37.50
-2y=-5.50
2y=5.50
y=2.75

Therefore, cost of eraser(y) = $2.75
And, cost of pen(x) = (21.25-4y)/3 = $3.41