Answers

2015-12-29T19:01:52+08:00
 let x = be the units digit
    3x = hundreds digit
3x -1 = tens digit

Equation:
x + 3x +3x - 1 = 20 

 7x - 1 = 20
      7x = 20 + 1
      7x = 21
7x ÷ 7 = 21 ÷ 7
        x = 3

Now, substitute:

           3 = units digit
3(3) = 9 = hundreds digit
 3(3) - 1 = 8 = tens digit


Therefore, the answer is (or the three-digit number is) 983.


Check:
(3) + 3(3) + 3(3) - 1 = 20
                 3 + 9 + 8 = 20

Hope it helped ☺
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  • Brainly User
2015-12-30T22:26:58+08:00
Units digit: x
Hundreds digit: 3x
Tens digit: 3x - 1
Sum of the digits = 20

Equation:
(3x) + (3x-1) + x = 20
3x + 3x + x - 1 = 20
7x = 20 + 1
7x = 21
7x/7 = 21/7
x = 3

Substitute x with 3:
Hundreds: 3x ⇒  3(3) = 9
Tens: 3x - 1  ⇒    3(3) - 1 = 8
Units: x = 3

ANSWER: The 3-digit number is 983.

Check:
Hundreds digit + tens digit + units digit = 20
9 + 8 + 3 = 20

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