Question 1134538
at least one tie is 1-(no ties)
P(no tie too tight)  is 0.75^20=0.0032 so 1-0.0032 is 0.997

for 1 tie it is 20*.25*.75^19=0.0211
for 2 ties it is 20C2*.0.25^2*0.75^18=0.0669
sum of those three is 0.0922, so more than two is the complement or 0.9078 or 0.908.

no tie is too tight is 0.0032 from above

at least 18 are not too tight means 18, 19, 20 aren't too tight, and that means that 2, 1,0 are too tight, and that is 0.0922