Answer: Either 70% or S=0.7x
Step-by-step explanation:
I'm unclear as to what the question really wants. A "rate of success" is simply an expected percentage of future shots that will score on a free throw. Since the only statistic we are given is the 70%, it would seem that would also be the rate of success for future shots.
If the question is seeking the actual number of successful free throws, S, in the next x shots, the expression would be:
S = 0.70x