All sides are equal in an equilateral triangle and the perpendicular bisects the side too.
so BC will be bisected and the segments be 5 each.
you can use Pythagoras theorem to find the altitude length, hypotenuse will be one side of the triangle.

$h^2=100-25=75$
$h=\sqrt{75}=5\sqrt3$
Because $385 for two years is 385+385=770
Twice a month for two years=24x2=48
So 770/48=$16.04
Final answer $16.04
Answer:
maybe the second equation i.e(10+1.2)x=24