Question

You have a total of 21 pens and pencils on your desk. You have 3 more pens than pencils. Write a system linear equations that represent this situation.

Answer 1

x + y = 21
x - y = 3
Adding the above equations, we get,
2x = 24
x = 12.
y = 21 - x
y = 21 - 12
y = 9.
Therefore,
No. of Pens = x = 12,
No. of Pencils = y = 9.

Answer 2

`x+y = 21\\\\ y= x+3`

Explanation:

Linear equation : An equation made by using two variables that represents a straight line on a graph.

Let x be the variable that denotes the number of pens and y be the variable that denotes the number of pencils.

Given : You have a total of 21 pens and pencils on your desk.

i.e.
`x+y = 21` (1)

You have 3 more pens than pencils.

i.e.
`y= x+3` (2)

Now , from (1) and (2) , we have

The system of linear equations that represents the given situation :

`x+y = 21\\\\ y= x+3`