Question 1097613
I would call the three consecutive positive integers
{{{n-1}}} , {{{n}}} , and {{{n+1}}} .
 
Five times the square of the largest number is
{{{5(n+1)^2}}} .
 
Two times the sum of the squares
of the other two numbers is
{{{2(n^2+(n-1)^2)}}} .
 
The question states that the first expression above
is greater than the second one by 75.
That can be expressed as
{{{5(n+1)^2=2(n^2+(n-1)^2)+75}}} .
 
We can simplify that equation and solve for {{{n}}} .
If we find one or more solutions that is/are positive and integer,
we almost have the answer,
because what we want to find is the sum of the
smallest and the largest of the three consecutive positive integers,
and that would be {{{(n-1)+(n+1)=n-1+n+1=2n}}} .
 
Solving {{{(n+1)^2=2(n^2+(n-1)^2)+75}}} :
{{{5(n+1)^2=2(n^2+(n-1)^2)+75}}}
{{{5(n^2+2n+1)=2(n^2+n^2-2n+1)+75}}}
{{{5n^2+10n+5=2(2n^2-2n+1)+75}}}
{{{5n^2+10n+5=4n^2-4n+2+75}}}
{{{5n^2+10n+5=4n^2-4n+77}}}
{{{5n^2+10n+5-4n^2+4n-77=0}}}
{{{n^2+14n-72=0}}}
{{{(n+18)(n-4)=0}}} --> {{{system(n--18,"or",n=4)}}}
The  only possible answer comes from the positive integer {{{n=4}}} ,
and the answer is {{{2n=2*4=highlight(8)}}}