Answer:

Step-by-step explanation:
Let l litre of 7 grams of salt per litre is combined with x litres of water which contains y grams of salt per litre to yield a solution with 2 grams of salt per litre.
Thus,
Salt in l litre + salt in x litre = salt in resultant mixture
7l + xy = 2(l +x)
7l + xy = 2l + 2x
7l - 2l = 2x - xy
5l = x(2-y)

Hence,
litres of 7 gram of salt per litre is mixed.
Answer:
![\sqrt[3]{2y^3} * 7\sqrt{18y} = 21(y^{\frac{3}{2}})(2^{\frac{5}{6}})](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B18y%7D%20%3D%2021%28y%5E%7B%5Cfrac%7B3%7D%7B2%7D%7D%29%282%5E%7B%5Cfrac%7B5%7D%7B6%7D%7D%29)
Step-by-step explanation:
The question is poorly formatted.
Given
![\sqrt[3]{2y^3} * 7\sqrt{18y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B18y%7D)
Required
Derive an equivalent expression
![\sqrt[3]{2y^3} * 7\sqrt{18y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B18y%7D)
Express 18 as 9 * 2
![\sqrt[3]{2y^3} * 7\sqrt{9 * 2y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B9%20%2A%202y%7D)
Split the expression as follows:
![\sqrt[3]{2y^3} * 7\sqrt{9} * \sqrt{2y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B9%7D%20%2A%20%5Csqrt%7B2y%7D)
Take positive square root of 9
![\sqrt[3]{2y^3} * 7*3 * \sqrt{2y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%2A3%20%2A%20%5Csqrt%7B2y%7D)
![\sqrt[3]{2y^3} * 21 * \sqrt{2y}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%2021%20%2A%20%5Csqrt%7B2y%7D)
![21*\sqrt[3]{2y^3} * \sqrt{2y}](https://tex.z-dn.net/?f=21%2A%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%20%20%5Csqrt%7B2y%7D)
The cube root can be rewritten to give:
![21*\sqrt[3]{2}*\sqrt[3]{y^3} * \sqrt{2y}](https://tex.z-dn.net/?f=21%2A%5Csqrt%5B3%5D%7B2%7D%2A%5Csqrt%5B3%5D%7By%5E3%7D%20%2A%20%20%5Csqrt%7B2y%7D)
![\sqrt[3]{y^3} = y^{3*\frac{1}{3}} = y](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7By%5E3%7D%20%3D%20y%5E%7B3%2A%5Cfrac%7B1%7D%7B3%7D%7D%20%3D%20y)
So, we have:
![21*\sqrt[3]{2} * y * \sqrt{2y}](https://tex.z-dn.net/?f=21%2A%5Csqrt%5B3%5D%7B2%7D%20%2A%20y%20%2A%20%20%5Csqrt%7B2y%7D)
Rewrite as:
![21y *\sqrt[3]{2} * \sqrt{2y}](https://tex.z-dn.net/?f=21y%20%2A%5Csqrt%5B3%5D%7B2%7D%20%20%2A%20%20%5Csqrt%7B2y%7D)
Split 
![21y *\sqrt[3]{2} * \sqrt{2} * \sqrt{y}](https://tex.z-dn.net/?f=21y%20%2A%5Csqrt%5B3%5D%7B2%7D%20%20%2A%20%20%5Csqrt%7B2%7D%20%2A%20%5Csqrt%7By%7D)
Collect Like Terms
![21y*\sqrt{y} *\sqrt[3]{2} * \sqrt{2}](https://tex.z-dn.net/?f=21y%2A%5Csqrt%7By%7D%20%2A%5Csqrt%5B3%5D%7B2%7D%20%20%2A%20%20%5Csqrt%7B2%7D)
Represent in index form

Apply law of indices




Hence:
![\sqrt[3]{2y^3} * 7\sqrt{18y} = 21(y^{\frac{3}{2}})(2^{\frac{5}{6}})](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B2y%5E3%7D%20%2A%207%5Csqrt%7B18y%7D%20%3D%2021%28y%5E%7B%5Cfrac%7B3%7D%7B2%7D%7D%29%282%5E%7B%5Cfrac%7B5%7D%7B6%7D%7D%29)
Formula for triangle perimeter is: a + b + c. In this scenario we have:
a = 3 feet 8 inches
b = 2 feet 10 inches
c = 4 feet
a + b + c =
= 3 ft + 8 in + 2 ft + 10 in + 4 ft =
= 9 ft + 18 in
We know that 1 foot is 12 inches, so we can simplify the result to this form:
10 ft + 6 in
or:
<u>10.5 feet</u>
Answer: The correct answer is 18ft
Step-by-step explanation: