Last night, Roberto spent 90 minutes doing homework, 2/3 hour reading, and 540 seconds making his lunch for the next day. How many more minutes did Roberto spend doing homework than he did reading and making his lunch?

41

Step-by-step explanation:

Ok, so the time for homework is already simplified to minutes.

2/3 of an hour is x/60

60/3 = 20

20*2 = 40

so 2/3 = 40/60

40/60 = 40 minutes

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540 seconds is..

540/60

54/6=9

9 minutes

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40+9 = 49

90-49 = 41

So, he spent 41 more minutes on homework than on making lunch and reading.

- 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

look at photo