What is the answer? how do i create two equations?

Let x = cost to rent a snorkel and y =  cost to rent a pair of fins

12x + 15y = 153
              x = 3y

substitute  x = 3y into 12x + 15y = 153

12x + 15y = 153
12(3y) + 15y = 153
36y + 15y = 153
51y = 153
y = 3

x = 3* 3 = 9

answer
It costs $9 to rent a snorkel

Delta airlines or untied airlines

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