A simple addition operation can get the answer. The date is delayed by 4 days, that is, it is increased by 4 days on the basis of the original date.

Therefore, it can be concluded that the original competition was 1 11+4 = 15, so the competition was postponed to15.

Extended data:

Vector subtraction:

1, vector subtraction in plane coordinate system:

Vector a=(x 1, y 1), vector (x2, y2),

Vector c= vector a- vector b,

c=(x 1-x2，y 1-y2).

2. Vector subtraction in space coordinate system:

Vector a=(x 1, y 1, z 1), vector (x2, y2, z2),

Vector c= vector a- vector b,

c=(x 1-x2，y 1-y2，z 1-z2).

Baidu encyclopedia-subtraction