Answer:
We must answer the question:
What number is founded 4 units to the left of 1?
You can find this number by the equation x = 1 - 4 = -3
then the answer is 3 (tres).
The squander question says:
which number is the opposite?
The opposite of a real number is the same number with the sign changed, so the opposite of 3 is -3 (menos tres).