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Find the value of the expression [tex][tex]$21 - 2a$[/tex][/tex] if [tex][tex]$a = 3$[/tex][/tex].

A. 27
B. 15
C. 16
D. 57


Sagot :

To find the value of the expression [tex]\(21 - 2a\)[/tex] when [tex]\(a = 3\)[/tex], follow these steps:

1. Substitute the given value of [tex]\(a\)[/tex] into the expression. Here, [tex]\(a = 3\)[/tex].

So, the expression becomes:
[tex]\[ 21 - 2 \times 3 \][/tex]

2. Perform the multiplication first, as per the order of operations (also known as PEMDAS/BODMAS rules).

Multiply [tex]\(2\)[/tex] by [tex]\(3\)[/tex]:
[tex]\[ 2 \times 3 = 6 \][/tex]

3. Subtract the result from [tex]\(21\)[/tex]:

[tex]\[ 21 - 6 = 15 \][/tex]

Thus, after performing these steps, the value of the expression [tex]\(21 - 2a\)[/tex] when [tex]\(a = 3\)[/tex] is [tex]\(15\)[/tex].

So, the correct choice is:

B) 15