I'm completely stuck on this! what is the gcf of 18 and 36

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

What are the solutions of the equation? 5z^2 + 9z - 2 = 0 a. 1, -2 b. 1, 2 c. 1/5, -2 d. 1/5, 2

About 9% of th population is hopelessly romantic. if 2 people are randomly selected from the population, what is the probability that at least 1 person is hopelessly romantic?