Help plz!!<3 I'm doing a quiz in K12

Does the problem involve permutations or? combinations? do not solve. the matching section of an exam has 4 questions and 7 possible answers. in how many different ways can a student answer the 4 ? questions, if none of the answer choices can be? repeated?

Which ordered pair (c, d) is a solution to the given system of linear equations- c+2d=13 -9c-4d=-15

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36