Solving proportions
[tex] \frac{1\3}{5} = \frac{a}{20} [/tex]

Answer:
a = 4/3
Step-by-step explanation:
1/3 a
----- = -----
5 20
Using cross products
1/3 * 20 = 5a
20/3 = 5a
Divide each side by 5
20/3 * 1/5 = 5a/5
4/3 = a