A is partly constant and partly varies as B .when B=14,and B =6,A=20.find A when B =3

so, are you studying the topic while you wait?

A is partly constant and partly varies as B ... A = mB + c
So, using their data,
6m+c = 20
14m+c = ??? (you left that out)
Plug in the other value for A, and then solve for m and c.
Then use them to find A when B=3

And next time you get all impatient, make sure your post is correctly delivered.