If Rob saves $5 for every $16 he earns, he is saving the folowing franction of his income: .
Then if his income equals $16, he will save .
If his income is $80, he will save
Another way to understand this problem would be to think that . Then, receiving $80 is the same as receiving 5 times $16. If he saves $5 for every $16 he receives, he would save 5 times $5 = $25.