He saves $ 1.75 each day from his allowance.
Explanation
The ratio of his savings and expenses is 7 : 5
Lets assume, his savings = 7x dollar and his expenses is 5x dollar
Given that, his daily allowance is $3. So....
[tex]7x+5x=3\\ \\ 12x=3\\ \\ x=\frac{3}{12}= \frac{1}{4}= 0.25[/tex]
So, the amount of his savings each day [tex]=7x= (7*0.25)dollar= 1.75 dollar[/tex]
