Answer:
The correct way to interpret the difference of a number divided by 6 and 5 equals 8 is
n/6 - 5 = 8. I believe that another tutor has misled you; there should be only one division, applying to n only.
6- 20
8- 30
10- 10
20- 2 Questions?
The answers are: 4.5 g and 56.25 g respectively.
Since the first type of measurement in this question is weight or mass, I'll suppose that the percentage concentration is % mass/mass. For that type of concentration measurement, just multiply the percentage by the total mass to get the mass of the wanted material.
So 150 g * 3% = 150 g * 0.03 = 4.5g
For the 8% solution with the same amount of dry substance, use the ratio of percentages, multiplied by the mass of the first solution to get the wanted amount of new solution:
3/8 * 150 g = 56.35 g
(3/5 + -1/4)/(7/10)
get a common denominator of 20
3/5 * 4/4 =12/20
-1/4 * 5/5 = -5/20
7/10 *2/2 = 17/20
replace
(12/20 - 5/20)/(14/20)
add the top
(7/20)/(14/20)
copy dot flip
7/20 * 20/14
7/14
1/2
