water cost $2 for 8 bottles orange juice cost a $1.50 for 3 bottles which is more expensive per bottle ​

I believe you can use ratios and multiply both of them like fractions to get the same amount of bottles and compare the prices fairly.

2:8 = 2/8
1.5:3 = 1.5/3

(2/8)3 = 6/24 or $6 per 24 bottles
(1.5/3)8 = 12/24 or $12 per 24 bottles

In conclusion, the latter ($1.50 for 3) costs more than the $2 per 8.

You can find the area of a rectangle by multiplying the length and height. so multiply 1/2*7/4(which is the simpler version of 1 3/4) and you get 7/8 as your answer.