Step-by-step explanation:

Isn't that simply asking you to compute 30% of 20?
30 x
----- = ------
100 20
100x = 600
x = 6
So, out of those 20 numbers, you would expect that 6 of them would begin with the digit 1.
Area of a triangle = base x height / 2
64 = base x height / 2
(multiply 2 on both sides)
128 = base x height
then if base= 16 and height = 8 then 16 x 8 = 128
thus the base is 16 which is twice the height:8