Answer:
1400
Step-by-step explanation
First I made a list of all of the first 7 carriages, so that's 125, 150, 175, 200, 225, 250, and 275. After adding those you get 1400.
The next number would be -15
Answer:
3(t+2)
Step-by-step explanation:
As with any problem involving division of fractions, you can invert the denominator and multiply.
Your knowledge of the factoring of the difference of squares helps. If that doesn't work for you, you can always use synthetic division or polynomial long division to find the quotient of (t^2-4) and (t-2).

Answer:
-4x + y + 6z
Step-by-step explanation:
Combine like terms (Terms with the same variable):
(2x + 5y - z) + (-6x - 4y + 7z)
Add straight across:
2x - 6x = -4x
5y - 4y = y
-z + 7z = 7z - z = 6z
-4x + y + 6z is your answer.
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Complimentary = 90 degrees
Supplementary = 180 degrees
Compliment of 51:
90 - 51 = 39 degrees
Supplement of 39:
180 - 39 = 141 degrees
The supplement of the compliment of a 51 degree angle is 141 degrees.