中一數學文字方程,求教!!!

(1) The total cost of a set of 5 comic books and a deductive fiction is $176. If the price of a deductive fiction is 3 times that of a comic book, find the price of a comic book.
(Let $x be the price of a comic book.)
The price of the deductive fiction is $3x.
5x + 3x = 176
8x = 176
x = 22
The price of a comic book is $22.


(2) Ken has a certain number of $2 and $5 coins. The number of $2 coins is 5 more than that of $5 coins. If the total value of the coins is $59, find the number of $2 coins that Ken has.
(Let x be the number of $2 coins Ken has.)
The number of $5 coins is x - 5
2(x) + 5(x-5) = 59
2x + 5x - 25 = 59
7x = 84
x = 12
Ken has 12 $2 coins.


(3) The sum of two numbers is 27. If 3 is added to twice of the smaller number, the result is equal to the larger number. Find the two numbers.
(Let x be the smaller number.)
The larger number is 27 - x.
3 + 2x = 27 - x
3x = 24
x = 8
27 - x = 19
The two numbers are 8 and 19.


(4) John spends $40 of his monthly pocket money to buy some stationery. Then he spends half of the remaining to buy a music CD. He still has $130 left. Find the amount of monthly pocket money of John.
Let $x be the amount of monthly pocket money of John.
(x-40)*0.5 = 130
x - 40 = 260
x = 300
The amount of monthly pocket money of John is $300.


(5) The sum of the ages of Mr Lee and his son is 53. 4 years ago, the age of Mr Lee is 4 times that of his son. Find the ages of each of them.
Let x be the age of Mr Lee.
Then 53 - x is the age of his son.
x - 4 = 4(53 - x - 4)
x - 4 = 4(49 - x)
x - 4 = 196 - 4x
5x = 200
x = 40
53 - x = 13
Mr Lee is 40 years old and his son is 13 years old.