What is the result of substituting for y in the bottom equation?
y= x-7
y = x2 + 2x - 4

x^2+x+3

Step-by-step explanation:

y=x-7

x-7=x^2+2x-4

x^2+2x-4-x+7

x^2+x+3

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m

ratio is 2 : 9

the answer is three

13.5 : 3