✔ 最佳答案
1.
6y-3(5-y)=21
6y - 15 + 3y = 21
9y = 36
y = 4
2.
(8y-9)+(15-2y)=6-18
8y - 9 + 15 - 2y = -12
6y = -12 -6
y = -18
y= -3
3.
4(3m/5)-2m-8 = 0
12m - 10m - 40 = 0
2m = 40
m = 20
SUB m = 20 into equation,
LHS = 4(3*20/5) - 2*20 - 8
= 4*12 - 40 - 8 = 48-48
= 0 = RHS
4.
設較便宜那種小貓值 x 元
4x + 3(x+3) + 7 = 100元
4x +3x + 9 + 7 = 100
7x = 84
x = 12
較便宜那種小貓值 12 元, 較貴那種值 15 元
5.
茶葉A每公斤成本是$30,茶葉B氣公斤成本是$20。如果把w公斤的茶葉A和(w+1)公斤的茶葉B混合起來,使每公斤的成本變成$24,求w。
30w + 20(w+1) = 24 (w+w+1)
30w + 20w + 20 = 48w + 24
2w = 4
w = 2
6.
設原來 x 粒玻璃珠
x - 1/2x - 1/6x - 1/7x = 16
42x - 21x - 7x - 6x = 16*42
8x = 672
x = 84
原來有 84 粒玻璃珠