Question 251262
let the three no.s be a,b and c with a being the smallest and c the largest.

now given c=a+10
and b=(a+c)/2 i.e., 2b=a+c

also a+b+c=42  but from above eq. we have a+c=2b

2b+b=42 implies 3b=42
so, b=14

and a+c=28  (as 2b=28)
now from the first point i.e., c=a+10 we have c-a=10 and also from the above one we have c+a=28,

adding them both we get 2c=28+10=38

so c=19
and a=9
and b=14