Question

sum of the two number is 21 and their difference is 3 find the numbers

Answer 1

x+y=21(1)
x-y=3(2)
x=y+3
put x in 1
y+3+y=21
2y+3=21
2y= 18
y=18÷2
y=9
x=12
y=9
12+9=21
12-9=3

Answer 2

Answer: x=12, y=9 are the two numbers whose sum is 21 and difference is 3.

Step-by-step explanation:

Concept: linear equations, in maths are those in which the variable's maximum power is one. A straight line is the only possible solution to a linear equation. Thus, a system of two linear equations in two or three variables that are solved simultaneously to arrive at a shared solution is known as a simultaneous linear equation.

RULE : If the signs are different, add the equations together. If the signs are the same, subtract them.

Step 1: let x and y be the two numbers. Now, we are given that,

1. x+y = 21
2. x-y = 3

Step 2: In order to solve them, we add the two equations 1 and 2 with each other since the signs are different for y in both the equations, such that,

     x+y=21

  +  x-y=3

_________

⇒ 2x = 24

⇒ x = 12

Hence, y = 21 - 12 = 9 (after putting the value of x on eq 1 and solve for y)

Final ans: So, the two numbers so obtained on solving the two equations, are 12 and 9.