Answer:
$19.95
Explanation:
The total cost for 3 pounds can be found using: 
1 pound + 1 pound + 1 pound 
We know that there is a coupon for 15% off one pound. Normally you pay for 100%, but since there is 15% off (subtracted), you only pay 85%. (100%-15%=85%) 
Multiply 85% and $7. 
85%* $7 
Convert 85% to a decimal by dividing 85 by 100. 
85/100= 0.85 
0.85 * $7 
Multiply 
$5.95 
Now we know that 1 discounted pound costs $5.85. The other 2 pounds are regularly priced at $7 each. 
1 pound + 1 pound + 1 discounted pound 
$7 + $7 + $5.95
$14 + $5.95 
$19.95 
3 pounds will cost $19.95