Question

Using the same algorithm:

• Start with a number and add 2 to it.
Double the result.
• Subtract 3 from that quantity.
If the function outputs a value of 21, what was the value of the input?

Answer 1

• let the number be x:

`• { \tt{ \dashrightarrow \: 2(x + 2)}}`

`• \dashrightarrow{ \tt{2x + 1}}`

Answer 2

Let input be x

`\\ \bull\tt\dashrightarrow 2(x+2)-3=21`

`\\ \bull\tt\dashrightarrow 2(x+2)=21+3`

`\\ \bull\tt\dashrightarrow 2(x+2)=24`

`\\ \bull\tt\dashrightarrow x+2=(24)/(2)`

`\\ \bull\tt\dashrightarrow x+2=12`

`\\ \bull\tt\dashrightarrow x=12-2`

`\\ \bull\tt\dashrightarrow x=10`