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18) Amina thinks of a number and subtracts [tex] \frac{5}{2} [/tex] from it. She multiplies the result by 8. The result now obtained is 3 times the same number she thought of. What is the number?

Sagot :

To solve the problem step-by-step, let's follow the instructions given in the problem.

1. Define the unknown number:
Let [tex]\( x \)[/tex] be the number that Amina thinks of.

2. Subtract [tex]\( \frac{5}{2} \)[/tex] from [tex]\( x \)[/tex]:
The expression for this step is:
[tex]\[ x - \frac{5}{2} \][/tex]

3. Multiply the result by 8:
The expression now becomes:
[tex]\[ 8 \left( x - \frac{5}{2} \right) \][/tex]

4. Set this equal to 3 times the original number:
According to the problem, the result obtained after multiplying by 8 is equal to 3 times the number [tex]\( x \)[/tex]. So, we set up the equation:
[tex]\[ 8 \left( x - \frac{5}{2} \right) = 3x \][/tex]

5. Simplify the equation:
First, distribute the 8 inside the parentheses:
[tex]\[ 8x - 8 \cdot \frac{5}{2} = 3x \][/tex]
Simplify the multiplication:
[tex]\[ 8x - 20 = 3x \][/tex]

6. Solve for [tex]\( x \)[/tex]:
To isolate [tex]\( x \)[/tex], subtract [tex]\( 3x \)[/tex] from both sides of the equation:
[tex]\[ 8x - 3x - 20 = 0 \][/tex]
Simplify:
[tex]\[ 5x - 20 = 0 \][/tex]
Add 20 to both sides:
[tex]\[ 5x = 20 \][/tex]
Divide both sides by 5:
[tex]\[ x = 4 \][/tex]

So, the number Amina thinks of is:
[tex]\[ x = 4 \][/tex]

Therefore, the number Amina thinks of is [tex]\( 4 \)[/tex].

Answer :

Let the number be x.

According to the given question,

8 (x - 5/2) = 3x

8x - 20 = 3x

Transposing 3x to LHS and -20 to RHS, we obtain

8x - 3x = 20

5x = 20

Dividing both sides by 5, we obtain

x = 4

Hence, the number is 4.