大約中3-中4既數學問題 急啊*0*

7. Let the number of adult tickets sold be x.
Then the number of concessionary tickets sold is 4x.
x + 4x = 1500
5x = 1500
x = 300
4x = 1200
The sum of money for the tickets sold is:
300 x $3.7 + 1200 x $2.3 = $3870

9. 22x+2 = 22x + 192
22x x 22 = 22x + 192
4 x 22x = 22x + 192
3 x 22x = 192
22x = 64
22x = 26
2x = 6
x = 3

4y+1 = 4y + 192
(22)y+1 = (22)y + 192
22y+2 = 22y + 192
y = 3

M.C.
2. 1 Australian dollar = 5.74 H.K. dollar
1 U.S. dollar = 7.78 H.K. dollar
100 U.S. dollars = 100 x 7.78 H.K. dollars = 778 H.K. dollar
= 778 / 5.74 Australian dollar = 136 Australian dollar
Answer is C.

3. Let the amount of money be P.
Simple interest is : P x 6% x n
Total amount compounded half-yearly is : P ( 1 + 3% )10 = 1.344 P
Compound interest is : 1.344 P – P = 0.344 P
P x 6% x n = 0.344 P
n = 0.344 / 6% = 5.7
Answer is D.

7. Perimeter of the square is 4x cm.
The perimeter of a rectangle is :
( x/4 + x/2 ) x 2 cm = ( 3/2 ) x cm
8 x ( 3/2) x = 4x + 96
12x = 4x + 96
8x = 96
x = 12
Answer is B.

8. ( by-1 – by+2 ) / by+1
= ( by/b – b2 by ) / ( b by )
= ( 1/b – b2 ) / b
= 1/b2 – b
Answer is A.