Respuesta :

Hello.

First, "twice a number" means we multiply 2 times that number.

Let the number be s.

Now, the sum of 2 times s and 5 is 21.

The product of 2 and s can be written like so:

[tex]\sf{2s[/tex]

Now, the sum of 2s and 5 is 21:

[tex]\sf{2s+5=21[/tex]

Subtract 5 from both sides:

[tex]\sf{2s=21-5[/tex]

[tex]\sf{2s=16}[/tex]

Now, divide both sides by 2:

[tex]\Large\boxed{\sf{s=8}}[/tex]

I hope it helps.

Have a nice day.

[tex]\boxed{imperturbability}[/tex]

x = 8

Step-by-step explanation:

Let the required number be x.

According to the given question,

=> 2x + 5 = 21

=> 2x = 21 - 5

=> 2x = 16

=> x = 16/2

=> x = 8

Hope it helps you!!