Answer:
15
Step-by-step explanation:
Using the formula:
[tex]P = 2 (a+b)[/tex]where P is the perimeter, b is base and a is side lengths
Solving for a:
[tex]a = \frac{P}{2} - b[/tex]
[tex]a = \frac{70}{2}-20[/tex]
[tex]a =15[/tex]
