Make r the subject of the formula

Each cookie sells for $0.50 sam spent $90 on baking supplies and each cookie cost $0.25 to make how many cookies does sam need to sell before making a profit formula: sales> cost

At the electronics store you have a coupon for 20% off up to 2 cds you buy for cds with the original cost of $10.99 each the sales tax is 5% what is the total cost of your purchase

What is the missing statement in step 4? ? rts ? ? vtu and ? rtu ? ? vts ? rts ? ? rvs and ? rtu ? ? stv ? vrs ? ? vru and ? usr ? ? usv ? vur ? ? vus and ? uvs ? ? sru