中一數學題(超急)

1. 3D/4 + 12 = 3D
3D/4 - 3D = -12
3D/4 - 12D/4 = -12
- 9D/4 = -12
-9D = -48
D = 48/9
D = 16/3

2. 2(A+5) - 3(A-3) = 4A
2A + 10 - 3A + 9 = 4A
- 1A + 19 = 4A
- 1A - 4A = -19
-5A = -19
A = 19/5

3. S/4 + S/5 = 18
5S/20 + 4S/20 = 18
9S/20 = 18
9S = 360
S = 40

4. father's age = y
y times (1 - 1/4) = 27
y times 3/4 = 27
y = 36
her father's age is 36
36 times 1/4 = 9
her age is 9.

Hope I helped. =]

1.3D over 4 + 12 = 3D
3D/4 = 3D -12
3D= 4 (3D-12)
3D= 12D- 48
9D= 48
D= 16/3

2.2(A + 5) - 3(A - 3)=4A
2A+10-3A+9=4A
5A=19
A=19/5

3.S over 4 + S over 5 = 18
20 x (S/4 + S/5) = 20 x 18
5S + 4S= 360
9S=360
S=40

4.Teresa's age is 1 over 4 of her father's.If she is 27 years younger than her
father,find her age.
Let Teresa'sage is A, her father age = 4A

4A-A=27
3A=27
A=9

Teresa is 9 years old.