Respuesta :

1117-1038=79, 79/2= 39.5, and then 1039+39.5=1078.5
The middle of 1038 and 1117 is 1077.5. 1117 - 1038 = 79. 79 / 2 = 39.5. 1038 + 39.5 = 1077.5.