Answer:
$13.65
Step-by-step explanation:
If one yard of material costs $3.9 and Alex wants to purchase 3.5 yards in total, we can solve this problem using rule of three, as we have the cost of one yard and just want to know the cost of more yards:
1 yard of material costs $3.9, so 3.5 yards of material costs X:
1 -> 3.9
3.5 -> X
X = 3.5 * 3.9 = 13.65
So, the total cost will be $13.65