using your f(x) I want to show you how to plug in different things itnot he function.
f(x) = -x + 4
f(1) = -1 + 4 = 3
f(2) = -2 + 4 = 2
f(m) = -m + 4
f(abc) = -(abc) + 4
f(h(x)) = -h(x) + 4
Does that help? what if you replaced h(x) with g(x)? Of course you already have that x so you could make it a little simpler as well. Let me know if you don't quite get it.
The driver's tip was $1.45 because the trip cost $8.55 (2.25+1.5+1.5+1.5+1.5+ 0.3) and Eric gave the driver $10 so to find how much the driver got tipped, you need to subtract 8.55 from 10 so $10 - $ 8.55 = $1.45
