I'm pretty sure the answer is 12.
Answer:
This equation is equivalent to 

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Answer:
B!
Step-by-step explanation:
we know that (x-5) and (y-6) must add up to 129 because 180-51 is 129
now let's plug in the values to see
51-5= 66 63-6 = 57
57+66 is 123, not this one, let's repeat the same step
77-5 is 72, 63-6 is 57, these added is 129
To find the amount of "tens" in a number, divide it by 10
8,000÷10=100
Answer: There are 800 tens