Yes, but as you plug whatever numbers you have into the equation parentheses won't be necessary.
<h3><u>The value of the larger number, x, is 57.</u></h3><h3><u>The value of the smaller number, y, is equal to 42.</u></h3>
x - y = 15
2x + 8 = 3y - 4
We can quickly get a temporary value for x by altering the original equation.
x - y = 15
<em><u>Add y to both sides.</u></em>
x = 15 + y
Now that we have a value of x, we can find the exact value of y.
2(15 + y) + 8 = 3y - 4
<em><u>Distributive property.</u></em>
30 + 2y + 8 = 3y - 4
<em><u>Combine like terms.</u></em>
38 + 2y = 3y - 4
<em><u>Subtract 2y from both sides.</u></em>
38 = y - 4
<em><u>Add 4 to both sides.</u></em>
y = 42
Now that we know the exact value of y, we can plug it back into the original equation.
x - 42 = 15
<em><u>Add 42 to both sides.</u></em>
x = 57
1/2 probability because 30 is half of 60.
Whenever you face the problem that deals with maxima or minima you should keep in mind that minima/maxima of a function is always a point where it's derivative is equal to zero.
To solve your problem we first need to find an equation of net benefits. Net benefits are expressed as a difference between total benefits and total cost. We can denote this function with B(y).
B(y)=b-c
B(y)=100y-18y²
Now that we have a net benefits function we need find it's derivate with respect to y.

Now we must find at which point this function is equal to zero.
0=100-36y
36y=100
y=2.8
Now that we know at which point our function reaches maxima we just plug that number back into our equation for net benefits and we get our answer.
B(2.8)=100(2.8)-18(2.8)²=138.88≈139.
One thing that always helps is to have your function graphed. It will give you a good insight into how your function behaves and allow you to identify minima/maxima points.