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▹ Answer
<em>d. 7/20</em>
▹ Step-by-Step Explanation
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Let 
be the volume of 20% solution, 
the volume of the 60% solution. We want a total volume of 400 mL in the final mixture, so
Each mL of either solution will contribute a corresponding concentration, and in the final mixture we want the 400 mL to have a 40% concentration, which means we should also have
Solve the system and we get 
.
$0.30x=y should be the answer because there is a 30cent fee for every day and x represents how many days it's kept therefore you would add 30 cents for every day it's kept so it's valid to say $0.30x=y becaue the 30 cents times the total of days it's kept = y (the toatl)
The legal in this following assignments is no other than e. measurable e = r. It is measurable because r contains a reference to a new rectangle(5, 10, 20, 30). So the <span>interfaces the rectangle class implements is measurable, we really can measure it by solving the rectangle sides.</span>
Volume=(4/3)pir^3
volume=288pi
288pi=(4/3)pir^3
divid eobht sides by pi
288=(4/3)r^3
multiply both sides by 3/4 to clear fraction (4/3 times 3/4=12/12=1)
216=r^3
cube root both sides
6=r
surface area=4pir^2
surface area=4pi6^2
surface area=4pi36
surface area=144pi in^2
