please explain formulas on getting answers for these please

A) P(someone wins)=1P(nobody wins) =1P(1 person losing)^3 =1(.83)^3 =10.571787 =0.428 (Rounding to three decimal places Probability that someone in the family of three wins is therefore 0.428 B) Probability of getting nothing=0.83 Probability of getting fries = (1-0.83)/2=0.085 Probability of getting sundae = (1-0.83)/2=0.085 Again, use the multiplication rule, Probability A gets nothing, B gets fries, C gets Sundae=0.83*0.085*0.085. Since there are 3! ways to permutate the give-aways, so P(A,B,C) in any order = 3!(0.83)(0.085) (0.085) = 0.03598, and if rounded = 0.0360 C) There are two cases: Two sundaes and 1 fries = 2+2+1=$5 or three sundaes, value = 3*$2 = $6. Calculate the probability of each of the two cases and add them (since they are mutually exclusive, so the sum of probabilities equals the probability of one case or the other)