What numbers add up to -5 and multiply to get -90

1. the following set of data represents the number of waiting times in minutes from a random sample of 30 customers waiting for service at a department store. 4 5 7 10 11 11 12 12 13 15 15 17 17 17 17 17 18 20 20 21 22 22 23 24 25 27 27 31 31 32 a. determine the number of classes and class interval.

Determine which expressions represent real numbers and which expressions represent complex number. asaaap! plis!

Why is causation so much more difficult to prove than correlation?