The average of 3 digit numbers such that xx0, 26x, xx5, 7x6, 2x1, x32 is 428.  Find the average of x+1, x+3, x+7.

\(\frac{23}{3}\)

Take unit digits of all the numbers:

0 + x + 5 + 6 + 1 + 2 = 8 

14 + x = 8

4 + x = 8                                (unit digit of 14 is 4)

x = 8 - 4 = 4

Now, average of x+1, x+3, x+7 is

= \(\frac{x+1+x+3+x+7}{3}\)

= \(\frac{5+7+11}{3}\)

= \(\frac{23}{3}\)