Jonathan's full name contains 8 letters for the first name and 10 letters for the surname. His sister's name has 5 letters for the first name and 10 letters for the second name. What's the total number of letters in their names?
Jonathan has 8 +10 = <<8+10=18>>18 letters in his name.
His sister has 5+10 = <<5+10=15>>15 letters in her name.
The total number of letters in their names is 18+15 = <<18+15=33>>33
#### 33