How do you evaluate \[3.5 - 5.2 - \left( { - 1.25} \right)\]?

Hint: The four basic arithmetic operations in Maths are: Addition, Subtraction, Multiplication and Division. The algebraic expression should be any one of the forms and hence to evaluate the given expression, we must know the rule of multiplying and subtracting the integers. Hence simplify the expression by removing the parenthesis, and simplify it by applying the rules.

Complete step by step answer:
Given,
\[3.5 - 5.2 - \left( { - 1.25} \right)\]
Simplify the expression by removing the parenthesis
\[3.5 - 5.2 - - 1.25\]
Notice how we have two negative signs next to each other. This implies that we have two negatives that are multiplying. Hence, we get: \[ - \cdot - = + \]
So, we rewrite the expression as:
\[3.5 - 5.2 + 1.25\]
Evaluating the terms, we get:
\[ = - 1.7 + 1.25\]
As, we have subtracted the first and second term and then we need to add the remaining term i.e., \[1.25\], hence after simplifying we get:
\[ = - 0.45\]
Therefore,
\[ \Rightarrow 3.5 - 5.2 - \left( { - 1.25} \right) = - 0.45\]

Note: The key point to evaluate the given expression is that we must know all the rules of multiplication and subtraction i.e., for multiplication: The product of two positive integers is a positive integer and the product of two negative integers is a positive integer. The product of positive and negative integers is a negative integer and for subtraction: if both the signs of the integers are positive, the answer will be the positive integer and if both the signs of the integers are negative, the answer will be the negative integer. If the signs of the integers are different, subtract the values, and take the sign from the largest integer value.