PLEASE HELP ASAP WILL GIVE BRAINLIES Question 17 (1 point) A group of six friends, which includes a set of twins, lines up for a picture. In how many ways can they be arranged if the twins do not want to stand beside each other?

Question 18 (1 point) In how many ways can the coach of the debating club select a team from six grade- eleven students and eight grade-twelve students if the team has four members, at least two of whom are in grade 12?

17: 480

(We first arrange all of the candidates except b in a line. This can be done in 5! ways. We now add b to the line. Since we now want to count the arrangements where b is positioned next to a, there are two possibilities for the position of b. (Either left of a or right of a).

There are thus 2⋅5! ways of arranging the candidates so that a and b are next to each other, and hence 6!−2⋅5!=4⋅5!=480 ways of arranging the candidates so that a and b are not next to each other)

18: i don't know sorry

step-by-step explanation: a reaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is:

step-by-step explanation: