A store marks up some shoes 60% to $128. What did they cost before the mark up?

Answer:$320

Step-by-step explanation:

60 = (a-128) / a x 100

60=100 (a-128) / a

Cross multiplying we get

60a=100 (a-128)

60a=100a-12800

Collect like terms

12800=100a-60a

12800=40a

Divide both sides by 40

12800/40=40a/40

320=a

a=320