Let $x$ and $y$ be nonnegative real numbers. If $x + y = 25$, then find the minimum value of $6x + 3y.$
First, let's isolate y in terms of x. We have
\(y=25-x\)
Now, let's subsitute this into the second equation. We have
\(6x+3(25-x)\\ 6x+75-3x\\ 3x+75\)
x can't be negative, so the smallest x can be is 0. Subbing 0 in, we get
\(3(0) + 75\\ 0+75\\ 75\)
So 75 is our answer.
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