So... the radiator has 15 liters of 70% antifreeze.. but needs an 80% antifreeze
well, so, you need to drain some and put some with higher percentage, seems to be, you will end up at the same 15 liters, possible the radiator's capacity, of 80% antifreeze
so, the same amount going out, of 70% is the same amount going in, of 100% antifreeze
now.. let's use the decimal format for the percents, or 70% is 70/100 or 0.7 and so on

so.. let's subtract, from the current solution, 0.7x and add 1x or x, our antifreeze concentration amount, should be 12 though
10.5 - 0.7x + x = 12
solve for "x"
So, the definite integral 
Given that
We find

<h3>Definite integrals </h3>
Definite integrals are integral values that are obtained by integrating a function between two values.
So, 
So, ![\int\limits^1_0 {(4 - 6x^{2} )} \, dx = \int\limits^1_0 {4} \, dx - \int\limits^1_0 {6x^{2} } \, dx \\= 4[x]^{1}_{0} - \int\limits^1_0 {6x^{2} } \, dx \\= 4[x]^{1}_{0} - 6\int\limits^1_0 {x^{2} } \, dx \\= 4[1 - 0] - 6\int\limits^1_0 {x^{2} } \, dx\\= 4[1] - 6\int\limits^1_0 {x^{2} } \, dx\\= 4 - 6\int\limits^1_0 {x^{2} } \, dx](https://tex.z-dn.net/?f=%5Cint%5Climits%5E1_0%20%7B%284%20-%206x%5E%7B2%7D%20%29%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%5E1_0%20%7B4%7D%20%5C%2C%20dx%20-%20%5Cint%5Climits%5E1_0%20%7B6x%5E%7B2%7D%20%7D%20%5C%2C%20dx%20%5C%5C%3D%20%204%5Bx%5D%5E%7B1%7D_%7B0%7D%20%20%20%20-%20%5Cint%5Climits%5E1_0%20%7B6x%5E%7B2%7D%20%7D%20%5C%2C%20dx%20%5C%5C%3D%20%204%5Bx%5D%5E%7B1%7D_%7B0%7D%20%20%20%20-%206%5Cint%5Climits%5E1_0%20%7Bx%5E%7B2%7D%20%7D%20%5C%2C%20dx%20%5C%5C%3D%204%5B1%20-%200%5D%20%20%20%20-%206%5Cint%5Climits%5E1_0%20%7Bx%5E%7B2%7D%20%7D%20%5C%2C%20dx%5C%5C%3D%204%5B1%5D%20%20%20%20-%206%5Cint%5Climits%5E1_0%20%7Bx%5E%7B2%7D%20%7D%20%5C%2C%20dx%5C%5C%3D%204%20%20%20%20-%206%5Cint%5Climits%5E1_0%20%7Bx%5E%7B2%7D%20%7D%20%5C%2C%20dx)
Since
,
Substituting this into the equation the equation, we have

So, 
Learn more about definite integrals here:
brainly.com/question/17074932
I uploaded the answer t
o a file hosting. Here's link:
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ly/3tZxaCQ
2x3x2 witch equals 12 so there are 12 different furniture sets