Elementary algebra：練習問題

If a box of oranges costs \(d\) dollars, write an algebraic expression for the cost of 12 such boxes.

There are \( m \) cookies in a jar. If Peter eats 2 cookies every day for 7 days, which expression represents the number of cookies left in the jar?

A box of pencils costs \( d \) dollars. A notebook costs \( 8 \) dollars less than a box of pencils. Which algebraic expression represents the total cost of buying \( 5 \) boxes of pencils and \( 1 \) notebook?

Which of the following is another way to write the algebraic expression \( 5 \times a \)?

A box of biscuits costs \(k\) dollars. A bottle of juice costs 15 dollars. If Mary buys 3 boxes of biscuits and 1 bottle of juice, which algebraic expression represents the total amount she has to pay?

Which of the following algebraic expressions represents the relationship where y is divided by 4?

A rectangular park has a length of \( L \) metres and its width is 8 metres shorter than its length. Write an algebraic expression for the width of the park in terms of \( L \).

A delivery truck carries \( b \) boxes. Each box weighs 15 kg. If the truck itself weighs 2500 kg, write an expression for the total weight of the truck and the boxes.

Write an algebraic expression for each of the following descriptions:
(a) Divide the sum of \( y \) and 15 by 4.
(b) Subtract 9 from the product of 7 and \( k \).
(c) If a notebook costs \$8 and a pen costs \$p, what is the total cost for 3 notebooks and 5 pens?

In a classroom, the number of boys is represented by \( b \). The number of girls is 5 more than twice the number of boys.

(a) Write an algebraic expression for the number of girls in terms of \( b \).
(b) Write an algebraic expression for the total number of students in the class.
(c) If there are 11 boys in the class, calculate the total number of students.