...the domain is the set of values that your independent variable can take. In this problem, you are given x = 10, so that's it! Your domain is just x = 10!
the range is the set of values that f(x) can take. You are just given that the minimum is -7. Therefore the range is y such that y is greater than or equal to -7.
So, note that I've used f(x), but this is NOT a function. A function produces 1 and ONLY 1 output per input value of x.
Here we have one input (x = 10) and an infinite set of values that y can take.
However, you can reverse this...what if we write that x is a function of y? In that case, the set of all numbers y such that y >= -7 becomes our domain, and x = g(y) = 10 becomes our range. No matter what the input value (as long as its greater than or equal to -7), our output is the single value 10.