The sum of the digits of a two-digit number is 9. if the digits are reversed, the new number is 9 more than the original number. find the original number.

45

Step-by-step explanation:

Let the original number be xy where y is unit and x is tens hence original number is 10x+y When reversed, the new number is yz hence 10y+x

We know that the original number plus 9 is the reversed number hence

10x+y+9=10y+x

9y-9x=9 which when simplified we obtain that

y-x=1 equation 1

Originally, we are told that the sum of x and y is 9 hence

y+x=9 equation 2

Solving equation 1, it means y=x+1

Substituting the above into equation 2

x+1+x=9

2x=9-1

2x=8

x=8/2=4

Since y=x+1 then y=4+1=5

Therefore, the original number, xy is 45

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40