First multiply 3.9 (cost of fabric per yard) by 4 (number of yards) to get 15.6. Then divide 3.9 by 2 (since we need half a yard) to get 1.95. Lastly add 15.6 plus 1.95 to get your answer, $17.55.
Since it costs $3.90 per yard, we need to multiply 3.90 and 4. The product is 15.60, but we still have half a yard left. Simply divide $3.90 by 2 to get the price of half a yard ($1.95). Now, add them together to get $17.55
