Guys i need help on this one

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

which of the following sets of data would produce the largest value for an independent-measures t statistic? the two sample means are 10 and 20 with variances of 20 and 25 the two sample means are 10 and 20 with variances of 120 and 125 the two sample means are 10 and 12 with sample variances of 20 and 25 the two sample means are 10 and 12 with variances of 120 and 125

Jeremy wants to determine the number of solutions for the equation below without actually solving the equation. which method should jeremy use?