Let:
x = Pounds of walnuts in the mix.
Each pound of walnuts costs $0.80. thus x pounds of walnuts cost 0.8x dollars.
Each pound of cashews costs $1.25 and the mix will contain 8 pounds of cashews, so the cost is 8*$1.25 = $10
The total cost of the mix is, therefore: 0.8x + 10 dollars.
We are also given the pound of mix costs $1.00 and we have a total of 8 + x pounds, so the total cost of the mix is 1*(8 + x) dollars.
Equating both costs:
0.8x + 10 = 1*(8 + x)
Operating:
0.8x + 10 = 8 + x
Subtracting x and 10:
0.8x - x = 8 - 10
Simplifying:
-0.2x = -2
Dividing by -0.2:
x = -2/(-0.2)
x = 10
Answer: 10 pounds

whatever the amounts of "x" and "y" are, they must add up to 5Liters
thus x + y = 5
and whatever the concentrated quantity is in each, they must add up to (5)(0.14)
notice, that we use the decimal notation for the amount of juice concentration, that is, 15% is just 15/100 or 0.15, and 14% is just 14/100 or 0.14 and so on, recall that "whatever% of something" is just (whatever/100)*something
thus

solve for "x", to see how much of the 15% juice will be needed
what about "y"? well, y = 5 - x
The scale of the map is equal to 250 miles per 1.7 feet. or 250m/1.7ft. set up as a fraction.
Divide 250 by 1.7 to get how many miles are equal to just 1 foot.
250/1.7 = 147.058824 miles per 1 foot
Multiply that times 3.06 feet (the distance between C and D on the map)
147.058824m/1ft x 3.06ft = 450m
The actual distance between City C and City D should be 450 miles.