PLEASE HELP I will give brainliest I promise only if it’s correct and if it’s not I will report because this is very important to me thanks

Step-by-step explanation:

1) Price of 8 pack of toothbrushes = $ 18.12

Price he paid after using coupon  = 18.12 - 3  = $ 15.12

Unit rate = Price he paid ÷ number of toothbrushes

              = 15.12 ÷ 8

              = $ 1.89

2) 0.5 hours = 30 minutes

Duration of guitar class on Monday = 30 minutes

Duration of guitar class on Tuesday = 1.5 hours = 1 hr 30 min

Duration of guitar class on Thursday = 2 hrs

Total duration  = 30 min + 1hr 30 min + 2 hrs

                         = 4 hrs

Amount paid for 4 hrs = $ 180

Rate per hour = 180 ÷ 4

                       = $ 45

- 2 + 10x³ - 21x² + 19x - 4

step-by-step explanation:

each term in the second factor is multiplied by each term in the first factor

x²(- 2x² + 4x - 1) - 3x(- 2x² + 4x - 1) + 4(- 2x² + 4x - 1) ← distribute

= - 2 + 4x³ - x² + 6x³ - 12x² + 3x -8x² + 16x - 4

collect like terms

= - 2 + 10x³ - 21x² + 19x - 4 ← in standard form