Terms are just names for objects inside the equation -- anything that isn't an operation. A coefficient the is the number a given term (variable) is being mulitpled by. In this case, -3 for y, and 1 for. x. We can deduce from this the start of the expression (x has no coeff. bc of multiplicative identity)
x - 3y
We know we are missing one term, and we also know that the third term cannot be constant, so it must be another variable. In this case I have chosen Z, in theory it shouldn't really matter but z is the best variable name in this case.
