Explanation:
Hey there!
Given;
The sum of two numbers is 45.
One of them is 27.
Let next number is "x".
So, Add "x" and "27" and show it is equal to 45.
Or, x+27 = 45
Therefore, x+27 = 45 is the required equation.
Now, solving unknown number.
~ Take "27" to right side and subtract it.
x= 45 - 27
X= 18
Therefore, next number is (x) = 18.
Hope it helps...