79×77/78+38×38/39
=（78+1）×77/78+（39-1）×38/39
=78×77/78+77/78+39×38/39-38/39
=77+77/78+38-38/39
=77+38+1/78
=115+1/78
=8971/78
=115
七十九乘以七十八分之七十七加上三十八乘以三十九分之三十八
79×77/78+38×38/39
=（78+1）×77/78+（39-1）×38/39
=78×77/78+77/78+39×38/39-38/39
=77+77/78+38-38/39
=77+38+1/78
=115+1/78
=8971/78
=115