Question 996701
What is the four-digit number
a, b, c, d 
in which the first digit is one-third the second,
a = {{{1/3}}}b
:
 the third is the sum of the first and second,
c = a + b
replace a with {{{1/3}}}b
c = {{{1/3}}}b + b
c = {{{4/3}}}b
Because we must have single digit integer solution, only two are possible
b=3 then c=4, and b=6, then c=8
:
 and the last is three times the second? 
d = 3b
From this we know that b is 3 or less to be single digit
therefore, from the last two statements:
b = 3, resulting in c=4
and
a = {{{1/3}}}(3) = 1
and
d = 3(3) = 9
:
Our number: 1349