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"
Common Examples of Irrational Numbers
Pi, which begins with 3.14, is one of the most common irrational numbers. ...
e, also known as Euler's number, is another common irrational number. ...
The Square Root of 2, written as √2, is also an irrational number.
C. Because it only gives the measure of angles on line p and not line q
Answer:
a = √10
Step-by-step explanation:
a² + b² = c²
a² + 9² = (√91)²
a² + 81 = 91
a² = 10
a = √10
hope this helps :)