Answer:
![[15: (3 \times 5) + 4] \times 8](https://tex.z-dn.net/?f=%5B15%3A%20%283%20%5Ctimes%205%29%20%2B%204%5D%20%5Ctimes%208)
Step-by-step explanation:
First of all, let us have a look at the rule for solving brackets/parentheses/algebraic operations.
The rule states that the expression must be solved in the following order:
B - Brackets (Innermost parentheses first, then the enclosing brackets are solved)
O - Of (for example 10% of 20)
D - Divide operation
M - Multiplication operation
A - Addition operation
S - Subtraction operation
So, we need to add a set of parentheses i.e. () and a set of brackets i.e. [] in the expression:
such that the result is 40.
Consider the expression: ![[15: (3 \times 5) + 4] \times 8](https://tex.z-dn.net/?f=%5B15%3A%20%283%20%5Ctimes%205%29%20%2B%204%5D%20%5Ctimes%208)
Let us try to solve the expression using the above rule:
![[15: (3 \times 5) + 4] \times 8](https://tex.z-dn.net/?f=%5B15%3A%20%283%20%5Ctimes%205%29%20%2B%204%5D%20%5Ctimes%208)
First of all, the innermost () will be solved:
![(3\times 5) = 15](https://tex.z-dn.net/?f=%283%5Ctimes%205%29%20%3D%2015)
Now, the expression becomes:
![[15: 15 + 4] \times 8](https://tex.z-dn.net/?f=%5B15%3A%2015%20%2B%204%5D%20%5Ctimes%208)
Now, 15:15 will be solved as 1
![[1+ 4] \times 8](https://tex.z-dn.net/?f=%5B1%2B%204%5D%20%5Ctimes%208)
Now, the outer [] will be solved:
![5\times 8 = 40](https://tex.z-dn.net/?f=5%5Ctimes%208%20%3D%2040)
Hence, the correct answer is:
![[15: (3 \times 5) + 4] \times 8](https://tex.z-dn.net/?f=%5B15%3A%20%283%20%5Ctimes%205%29%20%2B%204%5D%20%5Ctimes%208)