1.骑车速度x km/h
30/x+2=30/(x/1.5)
30/x+2=45/x
30+2x=45
x=7.5
2.(1) 今年水价x元
3600/x=1800/[x/(1+1/3)]+600
3600/x=1350/x+600
3600=1350+600x
x=3.75
(2) 3600*(1-20%)=3600*80%=2880
3.原来每天加固x米
600/x+(4800-600)/2x=9
600/x+2100/x=9
9x=2700
x=300
4.新涂料每千克的售价x元
100/(x+3)+240/(x-1)=(100+240)/x
100x(x-1)+240x(x+3)=340(x-1)(x+3)
100x^2-100x+240x^2+720x=340x^2+680x-1020
60x=1020
x=17