so the average of 5 number is 7 means if you add the number together, then divide the result by 5, you get 7 so
(t+r+x+y+z)/5=7
but we are only concered what the average is so we assume that all the numbers are the same
exg
(5x)/5=7
x=7
so lets say that x=7
so 5(7)/5=7
if we add 1 to them we are just adding 1 to (5(7))=1+35=36
so the average is
36/5=7 and 1/5 or 7.2