Translate the following sentence into an equation using n for the unknown number. Then solve for n. when 15 is decreased by three times a number, the result is 21
a.
15 - 372 = 21
n = -2
b.
312 - 15 = 21
n = -2
C.
31 - 15 = 21
n = 12
d.
15 - 3n2 = 21
n-2

Given:

15 is decreased by three times a number, the result is 21.

To find:

The equation for the given statement and solve it.

Solution:

Let n be the unknown number. Then,

Three times of a number =

15 is decreased by three times a number =

It is given given that the result after subtraction is 21. So,

Divide both sides by -3.

Therefore, the required equation is and its solution is . Hence, the correct option is (a).

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step-by-step explanation: