已知AC:AB:BC=3:4:5,AC+AB=18,求2BC-3AC

问题描述:

已知AC:AB:BC=3:4:5,AC+AB=18,求2BC-3AC

AC:AB:BC=3:4:5
AC=3k;AB=4k;BC=5k
AC+AB=18
7k=18
k=18/7
2BC-3AC
=10k-9k
=k
=18/7