Allegation is a method to find the ratio in which two or more indignant are mixed to produce a mixture or solution.
The equation represents the total liters of acid that are needed is,
Thus the option 3 is the correct option.
<h3>What is allegation?</h3>
Allegation is a method to find the ratio in which two or more indignant are mixed to produce a mixture or solution.
Given information-
A scientist needs 10 L of a solution that is 60% acid.
The percentage of two acid solution are 50% and 90%.
Variable<em> x</em><em> </em>represent the number of liters of the 50% solution.
Variable<em> y </em>represent the number of liters of the 90% solution.
Quantity of acid from 50% solution is 
liters, and quantity of acid from 90% solution is 
liters.
As the scientist needs 10 L of a solution that is 60% acid. Therefore the quantity of acid in 60 percent acid solution is,
Thus 6 liters of acid required by the scientist. As to get the 6 liters of acid from 50% and 90 percent solution, we need to add the amount of acid in these solutions.Thus,
This is the required equation.
Hence the equation represents the total liters of acid that are needed is,
Thus the option 3 is the correct option.
Learn more about the mixture and allegation here;
brainly.com/question/24372098
Plug in your values
Simplify
Simplify
Simplify by removing a 2 from every term
Simplify by taking the fraction apart
Change 
to 1
Simplify 
to 
