Aptitude question,find no of integral solutions


#1

#Apti
x>=1,y>=2,z>=3
x+y+z=18
No.of non -ve integral solution ?


#2

You can do this by basic counting x =1,then y can take 2 ,3,4 upto 14 ,13 values ,z value then become fixed 18 -(x + y),if x=2 then y can take 12 values … upto x = 13,so no of terms are 13 ,we have to found 13 + 12 + 11 …1 which is n(n+1)/2 = 91.