Matrix questions: augmented and dimensions?

Question

1 3 -1 10

2 8 0 22

-2 2 1 -3 augmented matrix; which operation should you perform next to lead to a solution of the system in as few steps as possible?

a. replace row 2 with some of rows 1 and 2

b replace row 2 with some of rows 2 and 3

c replace row 3 with some of rows 1 and 3

I think the answer is c, im still not sure

2nd question

what are the dimensions of the product of

|3 -7 4|

|5 8 9|

| 4 2|

|-1 9|

|4 6|

a 2x2

b 2x3

c The product is not defined.

I think its a 2x2, butI'mm not sure still

Answer 1

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Answer 2

for b i think it's a 2X3 because (from my math notes)

"the resulting matrix will have the same number of rows as matrix A and the same number of columns as matrix B