A) over the open interval (0,0.7) at what value of x is the tangent line to f horizontal? b) at what x value over the interval (0,2] does the graph of f have a relative min (refer to f'x in a)

Yeah so for B, since you have found the zeros of f'(x), you can then determine at which interval(s) of x (or at what x-values) that the range is smaller than zero (because at this point the graph of f has a relative min). Remember to compare with the (0,2] interval so that you can only take those x-values within the interval.
P/s: It is super hard for me to just write like that without anything to illustrate. Hope you understand :))

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