Answer:
Step-by-step explanation:

10 to the power of 3 is 1000, and 400 divided by 1000 is 0.4 because you move the decimal place over 3 in the number 400 to get 0.4.
Answer:
x = 5.5
y = - 6.5
Step-by-step explanation:
Let one of the numbers = x
Let the other number = y
x + y = - 1
x = y + 12 Put the second equation into the first one
y + 12 + y = - 1 Subtract 12 from both sides
y + y = - 1 - 12 Combine both left and right sides
2y = - 13 Divide by 2
2y/2 = - 13/1
y = - 6.5
x + y = - 1
x - 6.5 = - 1 Add 6.5 to both sides
x = 5.5
3 4/5 because when you make the denominators equal by multiplying 1/4 by 5 on both sides and 4/5 by 4 and both sides you will get 5/20 and 16/20