-60x^3 + 480, that’s what I got
You can multiply either the top or bottom equation by -1 so lets say you apply it to the bottom equation it’ll look like this:
-9x + 9y = 18
6x - 9y = 12
then the +9y and -9y will cancel out
-9x = 18
6x =12
then you add the two equations together
-3x = 30
divide both sides by -3
x = -10
Answer:
15.

16. 10 ml of 20% saline and 40 ml of 10% saline
Step-by-step explanation:
A chemist takes x ml of 20% saline and y ml of 10% saline. In total, he takes
x + y ml that is 50 ml, so

There are
ml of salt in x ml of 20% saline and
ml of salt in 10% saline. There are
ml of salt in 50 ml of 12% saline. Thus,

15. We get the system of two equations:

16. Solve this system. From the first equation:

Substitute it into the second equation:

Yes, y=-9x is proportional