Question 178269
Well, first a good question to ask might be what is the average so far?  That would be
{{{(5+5+3+5+4+5)/6=27/6=4.5}}}
So, so far he has averaged 4.5 servings of fruit a day.  So we need to up it to 5.  Let's call the number of servings of fruit he needs to eat on the last day x.  Then we want
{{{(5+5+3+5+4+5+x)/7=5}}}
Note that since we want the average to be at least 5, solving the equation equal to 5 will tell us the minimum number of servings he needs to eat.  So the first step would be to multiply both sides by 7.
{{{5+5+3+5+4+5+x=35}}}
Now, we combine like terms on the left hand side:
{{{27+x=35}}}
Last, subtract 27 from both sides
{{{x=8}}}
So he needs to eat at least 8 servings of fruit on the last day to average 5 for the week.