How do you write 680,705 in expanded form? ?

When you answer this can you explain

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

1. if events a and b are non-overlapping events, how do you find the probability that one or the other occurs? 2. what does it mean if p(a or b) equals 1?