Question 1164151
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how to find the number?the units digit of a two-digit number is three more than the tens digit.
The number is equal to four times the {{{highlight(cross(sun))}}} <U>sum</U> of the digits.Find the number.
(Hint:we can represent a two digit number as 10r+u.)
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<pre>
Following to the hint, we write 

    N = 10r + u.         (1)


We are given that  

    u = r+3              (2)

and

    N = 4*(r + u).       (3)


Replace N in the left side of (3) by 10r + u, according to (1).

    10r + u = 4r + 4u.    (4)


Replace "u" in both sides of (4) by (r+3), based on (2).  You will get then

    10r + (r+3) = 4r + 4*(r+3).


Simplfy and find "r"

    10r + r + 3 = 4r + 4r + 12

    11r + 3 = 8r + 12

     11r - 8r = 12 - 3

     3r       = 9

      r       = 9/3 = 3.


Thus r = 3  and  u = r+3 = 3+3 = 6.


Hence, the number is  10r+u = 10*3 + 6 = 36.


<U>ANSWER</U>.  The number is 36.
</pre>

Solved.