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put this solution on YOUR website!Let X be the people who ate breakfast, Y be the people who ate lunch
We know that
(a) x + y = 100
and that
(b) 3.50x + 5.00y = 428
for (a), I choose to rewrite it as y = 100-x
Thence we have for (b):
3.50x + 5.00(100 - x) = 428
3.5x + 500 - 5x = 428
-1.5x = - 72
x = 48 ate breakfast
y = 100 - 48 = 52 ate lunch
Check:
$3.50 x 48 + $5.00 x 52 = $168 + $260 = $428
The solution checks