[Aditya Ghosh]

Let, the cost of pen and pencil be x and y respectively (x>=0 , y>=0)

cost of 2 pens is Rs. 30 (Given)

<b class=””>∴ 2x=30

<b class=””><b style=”font-family: inherit; font-size: inherit; color: var(–bb-body-text-color);”> ⇒ <b style=”font-family: inherit; font-size: inherit; color: var(–bb-body-text-color);”>x=15

cost of 2 pens and 5 pencils is Rs. 80 <b style=”font-family: inherit; font-size: inherit; color: var(–bb-body-text-color);”>(Given)

∴ 2x+5y=80 ⟶eqn(i)

Putting the value of x=15 in eqn(i), we get

30+5y=80

<b style=”font-family: inherit; font-size: inherit; color: var(–bb-body-text-color); background-color: var(–bb-content-background-color);”>⇒ 5y=80-30

⇒ y=50/5

⇒ y=10

Hence, the cost of 1 pen is Rs. 15 and the cost of 1 pencil is Rs. 10.

[Aditya Ghosh]

1. Initially a variable x is assumed as per the given data.

2. The number is now multiplied by 3,

=> New number = 3*x = 3x.

3. The number is now added with 5 with the above product,

=> New number = 3x + 5,

4. In the final step another variable y is subtracted from the new number,

=> Final number = 3x + 5 – y.

5. The resulting number is 3x + 5 – y.

Therefore, the resulting number is 3x + 5 -y.