设个位数字为x
x+10(3x+1)-(10X+3X+1)=45
31X+10-13X-1 =45
18X+9 =45
18X =36
X =2
十位数字为:2*3+1=7 7*10+2=72
设水高x厘米
(40/2)的二次*60=30的二次x
24000 =900x
x =8/3
设进价为x元
900*0.9-40=1+0.1x
770 =1.1x
x =700
设个位数字为x
x+10(3x+1)-(10X+3X+1)=45
31X+10-13X-1 =45
18X+9 =45
18X =36
X =2
十位数字为:2*3+1=7 7*10+2=72
设水高x厘米
(40/2)的二次*60=30的二次x
24000 =900x
x =8/3
设进价为x元
900*0.9-40=1+0.1x
770 =1.1x
x =700