How to solve #4 using substitution/ elimination method

Which graph represents 2x-5y< 15

33% of college students say they use credit cards because of the rewards program. you randomly select 10 college students and ask each to name the reason he or she uses credit cards. find the probability that the number of college students who say they use credit cards because of the rewards program is (a) exactly two, (b) more than two, and (c) between two and five inclusive. if convenient, use technology to find the probabilities.

Which coefficient matrix represents a system of linear equations that has a unique solution ? options in photo*