Achemist is mixing a 30% salt solution with a 20% salt solution to make 35 l of a new solution that will contain 25% salt. how much of the 30% solution should the chemist use?

17.5 L

Step-by-step explanation:

x L  of  30% solution , has 0.30x salt

35 L of 25 % solution, has (0.25*35) salt

(35 - x)L  20% solution, has 0.20*(35 - x) salt

Mass of salt before mixing = mass of salt after mixing

0.3x + 0.2(35 - x) = 0.25* 35

0.3 x + 7 - 0.2x = 8.75

0.1x = 8.75 -7

0.1x = 1.75

x = 17.5 L

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

really really sorry if i'm

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