Question

the unit's digit of a two digit number is 5 more than the ten's digit. The number it names is 5 less than 3 times the sum of digits. What is the number?

Answer 1

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let :-

B = A + 5 ____________1

10A + B = 3(A + B) ___________2

Substitute 1 in 2

10A + A + 5 = 3(A + A + 5)

11A + 5 = 3(2A + 5)    

11A + 5 = 6A + 15

5A = 10

A = 2

Then we know that B is 5 more than that, so B
= 7.

num is 27. 

7 is five more than the 2.
27 is three times what we get when we add the digits

======= (2 + 7 = 9).

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