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

Answer:

$x+y = 21\\\\ y= x+3$

Step-by-step 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 :

$x+y = 21\\\\ y= x+3$