Explain how you will find the sum of 4.2 and 2.14

you find the sum by adding a "0" at the end of "4.2" and the stack add them (or however you can add them).

Step-by-step explanation:

 4.20

+ 2.14

=  6.34

A. 7 units

Explanation:
The given triangle is a right-angled triangle.
This means that we can apply the Pythagorean theorem relating the lengths of the sides a follows:
(hypotenuse)² = (first side)² + (second side)²

In the given we have:
hypotenuse = 25 units
first side = 24 units
second side is the one we want to find

Substitute with the givens in the above equation to get the missing side as follows:
(25)² = (24)² + (second side)²
(second side)² = (25)² - (24)²
(second side)² = 49

either: second side = -√49 = -7 > rejected as side length cannot be negative
or: second side = +√49 = 7 > accepted

Hope this helps :)