Please help I will mark brainlest

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

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?