Respuesta :

Mibo

Answer:

Step-by-step 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

LadyStrange

The correct option :

[tex] =\tt (a) \: 4[/tex]

Steps to derive correct option :

[tex] = \frac{x + 1}{x + 3} = \frac{15}{21} [/tex]

[tex] =( x + 1 )\times 21 = (x + 3 )\times 15[/tex]

[tex] = 21x + 21 = 15x + 45[/tex]

[tex] = 21x + 21 - 15x = 45[/tex]

[tex] = 6x + 21 = 45[/tex]

[tex] = 6x = 45 - 21[/tex]

[tex] = 6x = 24[/tex]

[tex] = x = \frac{24}{6} [/tex]

[tex] =\color{plum} \bold{x = 4}[/tex]

Let us now place 4 in the place of x and see if the substitution is equivalent to [tex] \frac{15}{21} [/tex] :

[tex] = \frac{4 + 1}{4 + 3} = \frac{15}{21} [/tex]

[tex] = \frac{5}{7} = \frac{15}{21} [/tex]

[tex] = \frac{5}{7} = \frac{15÷3}{21÷3} [/tex]

[tex] = \frac{5}{7} = \frac{5}{7} [/tex]

Therefore, the value of x in this proportion = 4

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