3題ｍａｔｈｓ題(方程)

Q.1 2[7x - (x+3)] = 5x+22
[7x - (x+3)] = 5/2x+11
(7x - x - 3)= 5/2x+11
6x - 3 = 5/2x+11
7/2x = 14
x = 14 * 2/7
x = 4

Q.2 x+9/7 - 3x-2/4 =5(x+4)
-2x + 9/7 - 2/4 = 5x+20
9/7 - 2/4 - 20 = 7x
(36-14-560)/28 = 7x
538/(28*7) = x
x= 269/98 or x = 2.74(correct to 2 d.p.)

Q.3 Let mother be y, the son be x,
y = 24 + x ------------- 1
y-8 = 4 (x-8) ---------- 2
sub 1 into 2,
24 + x - 8 = 4x - 32
x + 16 = 4x - 32
48 = 3x
x = 16
sub x = 16 into 1
y = 24 + 16
y = 40