Answer:
él te dirá
Explanation:
he will tell you -> él te dirá
1) "he" translates to "él"
2) decir = to tell 
The sentence is in the future tense. 
Because decir is an irregular verb, the stem change will be dir-
Then you'll have to add the future tense ending for 3rd person, which in this case would be -á
3) you= tu  
Because "you" is the indirect object (the receiver of the verb), an indirect object pronoun will be used. The indirect object pronoun for "you" is "te" 
Indirect object pronouns: (me, te, nos, le, les) 
4) he tell you -> él dirá te 
Now you must rearrange the sentence correctly to get: 
él te dirá