The sum of 10 and a number x is equal to 14.

10+x=14; x=4

10+x=14

-10     -10

The 10's cancel out

x=4

 10+x=14

Step-by-step explanation:

The word "sum" implies addition, so we know we are going to be adding some values. The next part of the sentence just give you your two values, 10 and a number (x). We know to add these two together because of the word sum. The final part of the sentence is "is equal to 14" this simply mean =14. Put all the pieces together and you get : 10+x=14