BD = BD ---------> reflexive property
Triangle ADB = triangle CDB ---------> SAS congruence postulate
Hope that helps.
10p^3=1960p
/10. /10
P^3=196
P=5.8
Set components equal:

From this we find:

Substitute and solve system:

The point where they intersect is:
978 x .05 = 48.9 should be the tax.