Which equation could be solved using this application of the quadratic formula?

The marked price of an article is 25% above its selling price and the cost price is 30% less than its marked price . find the discount percent and gain percent. only a brainlest can solve it i will mark you brainlest

Solve the following pair of equations for x and y: ax/b_ by /a= a +b; ax - by = 2ab

Can someone me and explain..will award brainlest!