maths求A and Y

30 = -10 +(100A÷y)

40 = 100A÷y
40Y =100A
A = (40Y÷100) <----1.

PUT 1. IN THE 2.

75 = -15+(225A÷y)

90 = 225(40Y÷100) ÷ Y
90Y = 9000Y÷100
90Y = 90Y
Y = 1

A = (40 X 1 ) ÷ 100
A = 0.4


不知道對不對-v-"

y不等於0

設y=r

A=2.5r

30= -10+(100A÷y)....(i)
40=100A÷y
2=5A÷y

75= -15+(225A÷y)....(ii)
90=225A÷y
2=5A÷y

∴(i)=(ii)
∴A=2y/5, y=5A/2
沒有足夠數據求A, y的數值