Question

The sum of 14 and a number is equal to 17

Answer 1

The sum of 14 and a number  is 14+x

we know that this equals 17, so: 14+x=17. 

Let's substract 14 from both sides: 

x=17-14

x=3

so the number is 3.

Answer 2

14+n=17

From this it follows that

n=3