Respuesta :
You want the 12g of sugar to be 1% of the whole solution.
So, say you add [tex]x[/tex] grams of water. The solution will be composed of 12 grams of sugar and [tex]x[/tex] grams of water, for a total of [tex] 12+x [/tex] grams.
So, the ratio "sugar/total" will be
[tex] \dfrac{12}{12+x} [/tex]
and we want this ratio to be 1%, i.e. 1/100:
[tex] \dfrac{12}{12+x}=\dfrac{1}{100} [/tex]
Multiply both sides by 100 and [tex] 12+x [/tex] to get
[tex] 1200 = 12+x [/tex]
Subtract 12 from both sides:
[tex] x = 1188 [/tex]
So, a solution composed of 1188 grams of water and 12 grams of sugar will be 99% water and 1% sugar.
The next exercise is just the same: you can build and solve the following equation
[tex] \dfrac{99}{99+x} = \dfrac{3}{4} [/tex]
(I used the fact that 75% is three quarters). You should find the solution x=33.
