What is the smallest two-digit integer $n$ such that switching its digits and then adding 3 results in $2n$

We can write

n = 10a + b

where a and b belong to {1, 2, 3, …, 9}.

Swapping the digits produces a new number

n' = 10b + a

and adding 3 to this number makes up 2n,

n' + 3 = 2n

or

(10b + a) + 3 = 2 (10a + b)

so that

19a - 8b = 3

Since we want n to be the smallest possible 2-digit number that meets the criteria, let's start with a = 1. Then solving for b, we find

19 - 8b = 3

16 = 8b

b = 2

So, the number we're looking for is n = 12.

Just to confirm, swapping the digits gives 21, and 21 + 3 = 24 = 2•12.

$25

step-by-step explanation:

25 - 4.50 = 20.5

20.5 / 2 = 10.25

10.25 + 10 = 20.25

20.25 - 12.50 = 7.75

therefore the answer is $25 as shown as the first number.

1.3

step-by-step explanation:

3x2=6   9x+6

bring down the 6 on both sides

6+6=12

12= 9x

divide by 9

12/9 =

1.3 =x