Time= 6 1/4= 25/4
Principal- Rs x
Rate=?
Rate=100 * Simple Interest
Rate= 100*3x*4 divided by x*8*25
Rate=6%
The answer is

In the choices; the coefficients 21, 32 and 10 are not perfect squares.
Y represent the total number of newspapers sold by Colby.
20:50 as 40:100
so the answer is 40%