Fthe range of the function f(x) = 7x – 2.7 is {14.1, 30.9, 41.4, 58.9, 68}, what is its domain?

You need to solve  5 equations  
1. 7x - 2.1 = 14.1
2. 7x - 2.1 = 30.9  and so on

1. 7x - 2.1 = 14.1
7x = 16.2
x = 2.314     so first number in the domain is  2.314

You can calculate the other 4 in the same way

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Distributive property