Graph three points on the number line: a point at -2 1/4, a point at the opposite of -2 1/4, and a point at the sum of -2 1/4 and it’s opposite.
-2 1/4
-(-2 1/4) = 2 1/4
-2 1/4 + 2 1/4 = 0
So on the number line, the three points would be at -2 1/4, 2 1/4, and 0.