A scientist has two solutions, which she has labeled Solutuion A and Solution B. Each contains salt. She knows that Solutuion A is 65% salt and Solution B is 90% salt. She wants to obtain 110 ounces of a mixture that is 75% salt. How many ounces of each solution should she use?

a = amount (in oz) of solution A

b = amount of solution B

The scientist wants a mixture of 110 oz, so

a + b = 110

Solution A consists of 65% salt, so each ounce of solution A contributes 0.65 oz of salt; similarly, each ounce of B contributes 0.9 oz. The mixture is supposed to consist of 75% salt, which amounts to 0.75 * (110 oz) = 82.5 oz of salt. So

0.65 a + 0.9 b = 82.5

Solve for a and b:

b = 110 - a

0.65 a + 0.9 (110 - a) = 82.5

0.65 a + 99 - 0.9 a = 82.5

0.25 a = 16.5

a = 66  ==>  b = 44

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1

27

step-by-step explanation: