Question 759578
1.  What is the number:
     It is a two digit number less than 50
Let {{{a}}} and {{{b}}} be the digits.
     
"The sum of its digits is 12" translates as {{{a+b=12}}}.
"Their difference is 4" translates as {{{a-b=4}}}.
That gives a a system of equations.
The system ----> the solution:
{{{system(a+b=12,a-b=4)}}} --> {{{system(a=8,b=4)}}}
WIth those two digits we can make {{{48}}} and {{{84}}}, and only
{{{highlight(48)}}} is less than 50
 
2.  what is the number:
      One of its digits is half the other
      The number is greater than 50
With only those two conditions, there is more than one solution.
To make the number is greater than 50, the tens digit must be 5 or greater, so it cannot be half of another digit.
It must be that the units digit is half of the tens digit.
So, the tens digit is at least 5 and is an even number.
It could be {{{6}}} or {{{8}}}, and the numbers could be
{{{highlight(63)}}} or {{{highlight(84)}}}.