Answer:
15
Step-by-step explanation:
4 x __ = 12
the blank would be 3, once you did it on one side you have to do it on the other side too
5 x 3 = 15
Another way you can do it is by...
= 
solve for x (cross multiply)
Answer:2x-5
Step-by-step explanation:
2.5 yards is $15 so you divide 15 by 2.5 and you would get the cost of each yard, which is $6 per yard :)