Let A be the number of apples Ali ate and S be the number of apples Sara ate.
We have: A + S = 80 apples
And: A = <<4=4>>4S
Which means: 4S + S = 80
So: 5S = 80
So the number of apples Sara ate is: S = 80 / 5= <<80/5=16>>16 apples
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