Answer
$-\displaystyle \frac{6}{11}$
Work Step by Step
The aim is, step by step, to isolate $a$ on one side of the equation.
...Multiply out the parentheses
$5a+15+4a-5=-2a+4$
$...$add/subtract like terms on the left side
$9a+10=-2a+4$
...Subtracting 10 from both sides removes it from the left side
...Adding 2a to both sides removes it from the right side
$9a+10=-2a+4\qquad.../-10+2a$
$9a+2a=4-10\qquad ... $simplify
$11a=-6$
...Dividing both sides with $11$ isolates $a$ on the left side.
$a=-\displaystyle \frac{6}{11}$
