Add one on both sides of the equation. You would end up with -6=x/3. You would then cross multiply, so -6 times 3 and 1 (the denominator for -6) times x and you would get -18=x
Answer:
First brand of antifreeze: 21 gallons
Second brand of antifreeze: 9 gallons
Step-by-step explanation:
Let's call A the amount of first brand of antifreeze. 20% pure antifreeze
Let's call B the amount of second brand of antifreeze. 70% pure antifreeze
The resulting mixture should have 35% pure antifreeze, and 30 gallons.
Then we know that the total amount of mixture will be:

Then the total amount of pure antifreeze in the mixture will be:


Then we have two equations and two unknowns so we solve the system of equations. Multiply the first equation by -0.7 and add it to the second equation:



+

--------------------------------------



We substitute the value of A into one of the two equations and solve for B.


Number 1 is B and number 2 I belive is C. I hope I'm rightt, and I hope this helps.