Please help me :( question below.

Question

The variable Z is directly proportional to X, and inversely proportional to Y. When X is 6 and Y is 6, Z has the value 12. What is the value of Z when X = 13, and Y = 10

Answer 1

Z = kX/Y, for some constant, k.

 

Since Z = 12 when X = 6 and Y = 6, we have 12 = k(6)/6.

 

So, k = 12

 

Therefore, Z = 12X/Y

 

So, when X = 13 and Y = 10, Z = 12(13)/10 = 15.6