Question

را آزرا
What is the value of x in the proportion?

Answer 1

The correct option :

`=\tt (a) \: 4`

Steps to derive correct option :

`= (x + 1)/(x + 3) = (15)/(21)`

`=( x + 1 )* 21 = (x + 3 )* 15`

`= 21x + 21 = 15x + 45`

`= 21x + 21 - 15x = 45`

`= 6x + 21 = 45`

`= 6x = 45 - 21`

`= 6x = 24`

`= x = (24)/(6)`

`=\color{plum} \bold{x = 4}`

Let us now place 4 in the place of x and see if the substitution is equivalent to
`(15)/(21)` :

`= (4 + 1)/(4 + 3) = (15)/(21)`

`= (5)/(7) = (15)/(21)`

`= (5)/(7) = (15÷3)/(21÷3)`

`= (5)/(7) = (5)/(7)`

Therefore, the value of x in this proportion = 4

Answer 2

Explanation:

Cross multiply on both sides

= (x + 1) (21) = 15(x + 3)

= 21x + 21 = 15x + 45

Bringing like terms on one side

21x - 15x = 45 - 21

= 6x = 24

x = 24/6 = 4

Option A is the correct answer