To find your answer you could type in the cost and multiply it by the tax rate, so $0.72 X $0.06(The tax rate )= $0.0432
You then subtract 0.0432 from 0.72 and get 0.6768
rounded it would be $0.68
Hope this is right..
2x+5x-4=31
7x-4=31
7x=35
X=5
ST=5x-4= 5.5-4=25-4=21
