Write 0.84 as a fraction in simplest form

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

Find the difference (8ab+a+2) - (3ab+6)

15/16 as a decimal rounded to the nearest hundredth