Answer:
The Answer is: 47 1/4
Explanation:
11/8a + 5/4a = 18
Create a common denominator for he coefficient of a:
11/8a + 2/2 * 5/4a = 18
11/8a + 10/8a = 18
21/8a = 18
Multiply both sides by the inverse of 21/8:
8/21 * 21/8a = 18 * 21/8
a = 378/8 or 189/4 or 47 1/4