A radio is on sale for $50. If this price represents a 10% discount from the original price, what is the original price to the nearest nickel?

Ok, so the discount is given in a percentage, in this case 10%. The sale price is going to reflect 10% of the original price minus the discount, so ...

Sale $ = original$ - original $ x. 10

If we use some algebra, we can reorganize the equation to solve for the original price ...

Sale $ = original$ - original $ x. 10

Sale $ = original$ (1 -.10)

Sale $ = original$ x. 90

original$ = sale$/.90

So now we can plug in our values

original price = 50/.90

original price = 55.55555 = $55.55 to the nearest nickel