The answer is 5.2 because if you do 12.60 - 10 it’s 2.6 so you add another 2.6 because it’s 2.6 for a half a pound so if you add the two half of pounds it will add up to one pound so it will be 2.6 + 2.6= 5.2 so basically 5.20$
Amount of tax paid = 43-40 = 3
Tax rate = 3/40 = 0.75
0.75 x 100 = 7.5%
Tax rate = 7.5%
In a direct proportion, the equation can be set up as
y = kx
k = y/x
k = 6/20
k = 0.3