Operations with natural numbers

Write the numerical expression corresponding to each statement and work out its value:

1. a) Three times the sum of eight and five.

1. b) Twice twenty minus the quotient of twelve divided by four.

1. c) The difference between the product of six and three, and the number seven.

In a comic shop, a teenager buys $3$ manga books at $8$ € each and $2$ posters at $5$ € each. If he pays with a $50$ € note, how much change should he receive? Express all the calculations in a single line.

Work out the result of the following combined operations, paying attention to the order of operations:

1. a) $25 + 5 \cdot 4 - 10$

1. b) $36 : 6 + 2 \cdot 7$

1. c) $18 - 12 : 3 + 4$

Work out the result of the following combined operation step by step, respecting the order of operations:

$15 \cdot (13 - 3^2) + 4^2 : \sqrt{64} - 2 \cdot 5$

A cinema has a screen with $12$ rows of $18$ seats each. For a premiere, tickets for the first $4$ rows (VIP area) are sold for $15$ € and the remaining tickets for $9$ €. If all seats have been sold, what was the total revenue for the screen?

Apply the distributive property to factorise out the common factor and work out as quickly as possible the value of the following store billing calculation:

If the total result is to be divided into bags containing $5^3$ items each, how many bags will be filled? Express the process using powers.