<h3>The terms 4x and 5y has different variable present in it. 
</h3>
<em><u>Solution:</u></em>
Given that,
<em><u>The reason is:</u></em>
When we are adding terms which has exactly the same variables, we must add the constants and let the result stand with variable
Which means,
4x + 10x = 14x
But,
We cannot add terms that has different variable
Which means,
4x + 5y
Here, both the terms 4x and 5y has different variable present in it. Hence they cannot be added together