To find the minimum value of the function f(x), you should find the value of x which has the minimum value of y, so we will use the differentiation to find it
Differentiate f(x) with respect to x and equate it by 0 to find x, then substitute the value of x in f(x) to find the minimum value of f(x)
It will be 5.15-w= minimum wage in 1996. Your keyword in that word problem would be when they said that 5.15 was w more than the minimum wage in 1996. I hope I helped ya :)