5分之3÷25分之7+5分之2÷25分之7
=3/5÷7/25+2/5÷7/25
=(3/5+2/5)÷7/25
=1÷7/25
=25/7
12×7又15分之8-1又6分之5
=12×113/7-11/6
=(12×113×6-11×7)/(6×7)
=(8136-77)/42
=8059/42