Solve using substitution.
-7x + 9y = 20
y = 10

x=10

Step-by-step explanation:

1. substitute y for 10 getting -7x +9(10)=20

2. 9(10)= 90

3. with -7x+90=20 subtract 90 on both sides getting -7x= -70

4. then divide by -7 on both sides getting x=10

5. to check u substitute x with 10 and y with 10 getting -7(10)+9(10)=20. then multiply and add/subtract to get 20=20

answerthe vertex form

step-by-step explanation:

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