<PRE><B>Question 602717</B>
Greg bats in 7 cricket matches, in the 8th match he makes 9 runs and his average decreases by one.
 How many runs has he made in all?
:
Let x = number of runs in all
then
(x-9) = number of runs in the first 7 matches
:
7 match average - 1 = 8 match average
{{{(x-9)/7}}} - 1 = {{{x/8}}} 
multiply by 56 to clear the denominators
8(x-9) - 56 = 7x
8x - 72 - 56 = 7x
8x - 128 = 7x
8x - 7x = 128
x = 128 runs in all</PRE>