the sum of the digit of a two digit number is 7. the ten digit is 3 more then the one digit. need formula?

Unit digit (y) in terms of tens digit (x):

x + y = 7

y = 7 - x

x = y + 3

y = x - 3

Tens digit (x):

7 - x = x - 3

2x = 10

x = 5

Unit digit—1st equation:

= 7 - 5

= 2

Answer: 52 is the number.

Call the first digit, the one as you name it, X. Call the second digit, the ten digit, Y.

So X + Y = 7. Also, Y = X + 3. You have two equations and two unknowns.

Using the Y = X + 3, substitute that in the first equation for Y.

You get: X + (X + 3) = 7. 2X + 3 = 7. 2X = 4. X = 2.

Using X = 2, put that value in either equation and solve for Y.

X + Y = 7. Y = 7 - X. Y = 7 - 2 = 5.

Answer: Your number called XY is 52. Add the two digits to get 7 and the 5 is 3 more than the 2.

a = ten digit

b = one digit

number we search is ab

we have :

a+b =7 (sum of the digit of a two digit number is 7)

a =b+3 (ten digit is 3 more then the one digit)

replace a by b+3 in first equation :

b+3+b = 7 => 2b = 7-3 = 4

b= 2

and a=b+3 = 2+3=5

number is 52

enable x = gadgets digit enable y = tens digit the unique variety is comparable to 10y + x The reversal of the digits leads to 10x + y (10y + x) - 27 = 10x + y x + y = 7 x = 7 - y 10y + (7 - y) - 27 = 10(7 - y) + y 9y - 20 = - 9y + 70 18y = ninety y = 5 x = 2 the unique variety is fifty two the hot (reversed digits) variety is 25 examine QED

Let the units digit be x.

Tens digit = x + 3

Sum of digits = Units digit + Tens digit = 7

x + x + 3 = 7

2x + 3 = 7

2x = 4

x = 2

So, the units digit is 2.

Tens digit = x + 3 = 2 + 3 = 5

So, the number is 52.

Hope this helps.

also, the non-algebraic way is

if the number adds up to seven, and one has three less than the other one, add the three to the seven-which is 10. divide that by two, so each is 5, but the second number is 3 less than the first, and you added it to make ten, now you have to subtract it from your answer so instead of 55 you subtract 3 from the second 5 and get 52

2 numbers well use X and Y, x for the number in the ones and y fot he number in the tenths place.

so, we know that when these 2 numbers are added you get 7 so we can say

x+y=7

but you also know that the tenths number is bigger by 3 so we can say that

x+(y+3)=7

so now we have

x+ y =7

x+(y+3)=7

you can now solve by substitution or cancellation or matrix or whatever level math you are in...

'x' is units place and 'y' is tens place

x+3=y---------1

x+y=7---------2

substitute 1 in 2

x+(x+3)=7

2x+3=7

2x=7-3

2x=4

x=4/2

x=2

x+3=y

2+3=y

y=5

the number is 52