Your two equations are at the top, in the box is what each variable represents. Below the box is total liters of the 15%, which is going to equal the total liters for 10% plus the total liters for 25%. Make your percentages into decimals. There’s a total of 30 liters so, x+y needs to equal 30. Isolate a variable, I chose y, you can do either or (isolating x would be more math). Y is going to equal 30-x, substitute that for the Y in the second equation, then you need to distribute 0.25 into 30-x. Then it’s simple math, subtract 7.50 from both sides, add like gets, divide both sides by -0.15, making x=20.
