999 I think... let me know if that is correct:)
The variables are: x, y
The constant is: 4
The coefficients are: 5, 3
The exponent is: y^2
Answer:
seiscientos noventa y seis millones quinientos cuarenta y tres mil noventa y ocho
So say, we add "x" of the 60% saline solution, now, how much salt is in that solution? now 60% is salt but the rest is something else, but only salt is 60% of "x", or (60/100) * x, or
0.6x.
likewise, for the 10 Liters, if only 50% is salt, then is just (50/100) * 10 or
5.
now... let's check the water whilst we add "y" amount, the water has no salt at all, freshwater for that matter, so, salinity is 0%. or (0/100) * y or
0.

I believe the slope is 0 because it they are both horizontal lines? I may be wrong though.