Luis has $70. He wants to buy a new pair of shoes that costs $90. He asks his mother to borrow him some money. How much will he owe his mother after he buys the shoes?

How many liters of peroxide should be added to 12 liters of an 8% peroxide solution so that the resulting solution contains 16% peroxide?   original added new amount of peroxide 0.96 liters x 0.96 + x amount of solution 12 liters x 12 + x 0.18 liter 1.14 liters 1.92 liters 2.10 liters