Answer:
The answer is
[tex] \frac{2s}{n} - l = a[/tex]
Step-by-step explanation:
[tex]s = \frac{n}{2} (a + l)[/tex]
multiply both sides by 2 to get
[tex]2s = n(a + l)[/tex]
divide both sides by n to get
[tex] \frac{2s}{n} = a + l[/tex]
subtract L from both sides to get the answer
[tex] \frac{2s}{n} - l = a[/tex]