3.
Three different interpretations of an 8% sales tax? Odd question.
8%, 8 percent, literally means "8 per 100". For each $100 item you purchase you pay an additional $8 in tax.
8% = 0.08, the factor applied to the price to determine the tax.
8%=8/100, you pay 8 cents in tax for every 100 cents in sales
4.
Just because the ratio is 5:7 doesn't mean the total is 5+7=12. Non zero factors don't change a ratio, e.g. 5:7=50:70.
5.
b/g=5/7
The fraction of boys is b/(b+g) which if you've done these a few times you can immediately write down as 5/12. Let's solve it like its our first time,
![g = \frac 7 5 b](https://img.qammunity.org/2020/formulas/mathematics/middle-school/92a1go7efbuq9gnox3davx6si4akjj42lb.png)
![(b)/(b+g) = (b)/(b + \frac 7 5 b) = (1)/(1 + \frac 7 5) = (1)/((12)/(5)) = (5)/(12)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/emc1q3qe4g7io3b0jx5ta966xdh89ifyy7.png)
Similarly the fraction of girls is 7/12.