Question 540695
With sum of digits problems, you have to keep in mind that the variables we use are "standing" beside each other, not multiplying.  So, if we define the two-digit number as 'xy' then we mean 'x' is standing next to 'y', not that we are multiplying x*y.
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xy has the value 10*x + y because the 'x' is in the tens place and 'y' is in the ones place.
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We are told:
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x+y = 10
y = x+6
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Substitute y = x+6
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x + x+6 = 10
2x = 4
x = 2
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y = x+6
y = 8
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The number is 28.
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Done.