ok, so we are using the binomial distribution, for which the formula is, i'm sure you're familiar with what the variables mean, so i won't define them,

so for this set of questions, n = 25 always.

for (a), you want , here we have p = 2/38. you got that i think. hope your calculations are correct

for (b) you're not correct. here we want , p = 2/38 also here.

for (c) you want . here p = 18/38

for (d) you want . here p = 18/38