Mr. sinofsky used 5/8 of a tank of gas on a trip to visit relatives for the weekend and another 1 half of a tank commuting to work the next week. he then took another weekend trip and used 1/4 tank of gas. how many tanks of gas did mr. sinofsky use altogether?

Get all the fractions to have a common denominator. The common denominator is 8. 1/2 will turn into 4/8, and 1/4 will be 2/8. Add them all up and you will find he used 11/8 tanks of gas which can simplify into 1 and 3/8 tanks of gas

The answer to your question is:  (x³ - 5) (x + 4)

Step-by-step explanation:

x⁴ + 4x³ - 5x - 20      /     x + 4                x = -4

                  1     4     0     -5     -20           -4

                      -4       0     0    +20

                   1    0      0    -5       0        =   x³ - 5

Finally   (x³ - 5) (x + 4) = x⁴ + 4x³ - 5x - 20