1. The problem is to evaluate the expression: $18 + 11 + 5 - 8$. 2. The order of operations for addition and subtraction is from left to right. 3. First, add $18 + 11 = 29$. 4. Then add $29 + 5 = 34$. 5. Finally, subtract $8$ from $34$: $34 - 8 = 26$. 6. Therefore, the value of the expression is $26$.