Set up an equation and solve it to find the unknown number:
3 is added to three-fourth of a number to get 21.

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Solution

Let the number be z.
According to the question, $3 + \frac{3}{4} z = 21$
$\Rightarrow \frac{3}{4} z = 21 - 3 \Rightarrow \frac{3 z}{4} = 18 \Rightarrow 3 z = 18 \times 4 \Rightarrow 3 z = 72 \Rightarrow z = \frac{72}{3} \Rightarrow z = 24$

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Set up an equation and solve it to find the unknown number: 3 is added to three-fourth of a number to get 21.

Let the number be z. According to the question, 3+34z=21 ⇒34z=21−3⇒3z4=18⇒3z=18×4⇒3z=72 ⇒z=723⇒z=24

Set up an equation and solve it to find the unknown number:
3 is added to three-fourth of a number to get 21.

Let the number be z.
According to the question, $3 + \frac{3}{4} z = 21$
$\Rightarrow \frac{3}{4} z = 21 - 3 \Rightarrow \frac{3 z}{4} = 18 \Rightarrow 3 z = 18 \times 4 \Rightarrow 3 z = 72 \Rightarrow z = \frac{72}{3} \Rightarrow z = 24$