Question 975322
I am assuming that coffee and tea were the only beverages being served.
Otherwise, we cannot solve the problem.
 
If 27% of the guests didn't drink anything, then
100% - 27% = 73% drank either coffee or tea, or both.
Since 70% drank coffee, 73% - 70% = 3% must have drunk only tea.
The other 65% - 3% = 62% of the tea-drinking guests drank both beverages (coffee and tea).
{{{x}}}= number of guests that came for the party
{{{"62%"=62/100=0.62}}} of those {{{x}}} guests is {{{0.62x}}}
{{{0.62x=248}}}--->{{{x=248/0.62}}}--->{{{highlight(x=400)}}} .
So, {{{highlight(400)}}} guests came for the party.
 
CHECKING:
Of those {{{400}}} guests, 27%, or {{{0.27*400=108}}} , drank nothing;
70%, or {{{0.70*400=280}}} , drank coffee,
and 65%, or {{{0.65*400=260}}} , drank tea.
If we add all those numbers up, we get
{{{108+280+260=648}}} .
Since there were {{{400}}} guests, that means that
{{{648-400=248}}} guests were counted twice,
and that is because they drank both: tea and coffee.