Answer:b=-10.5, a=31.5
Step-by-step explanation: 3b=-a , -3b=a
a+b =21
-3b+b = 21
-2b=21
b=-10.5
a=-3b
a=-3*-10.5=31.5
Answer:

Step-by-step explanation:
Answer:
(-5,5)
Step-by-step explanation:
Answer: Use the coordinates (0,-7)
Step-by-step explanation:
Answer:
Use the image as an example
Step-by-step explanation:
Use this image as an example to solve it may help.
Hopefully this helps:)