Your graph of f(x)= is the parent function. What you need to know for this graph what the stretch or compression is and what the flip is. When you flip somehting over the x-axis, which is g(x), your is negative. Also, since your graph gets skinnier, the number before the x would be a whole number, with no fractions. The only answer that fulfills this is answer choice D.
If [ 2x + 6y = 18 ] was the equation you were supposed to graph, then #3 is the way to go. If it was some other equation, then you would have to slog through BOTH #1 and #2 tobe sure.