While you cannot solve 946x+642y=911 for numerical values of x and y, you can indeed solve 946x+642y=911 first for x and then for y:
-911 - 642y
For x: 946x+642y=911 becomes 946x = 911 - 642y, or x = ------------------
946
911-946x
For y: 946x+642y=911 becomes 642y = 911-946x, or y = ---------------
642
Let, the numbers are: x, (24-x)
Let, P(x) denote their products. Then, we have:
P(x) = x(24-x) = 24x - x²
P'(x) = 24-2x
P''(x) = -2
Now, P'(x) = 0 ⇒ x = 12
Also,
P''(12) = -2 < 0
So, By second derivative test, x = 12 is the point of local maxima of p. Hence the product of the numbers is the maximum when the numbers are 12 and (24-12) = 12
So, In short that numbers would be 12,12
Hope this helps!
In case the user wants to see workings. These problems can easily be solved on a calculator, but can we work them out in our heads? ;)
9.34-3.029
=9.340-3.029
=9.340-3.000-0.029
=6.340-0.029
=6.311
