Final answer:
The probability of Sushil winning a tennis match based on his previous record is 21/32, as probability is determined by the ratio of wins to total matches played.
Step-by-step explanation:
The question asks to estimate the probability that Sushil wins a tennis match based on his previous record of winning 21 out of 32 matches. The answer is found by dividing the number of matches won by the total number of matches played. Probability is calculated as the ratio of the number of favorable outcomes to the total number of possible outcomes. In this case, the probability of Sushil winning a match is 21 out of 32, or in fractional form, 21/32.