So we have the following system of equations:

We need to solve it by substitution. This means that we have to take the expression for x given by the second equation and replace x with it in the first equation:

So y=-1. If we use this value in the second equation:

So we have x=2 and y=-1 which means that there's one solution. Then the correct answer is A and the solution is (2,-1).
Answer:
1 5 10 10 5 1
Step-by-step explanation:
The complete question has been attached as an image.
Looking at the triangle, we see a pattern. The first level we have 1, in the next level we have 1 1, the next evel we have 1 2 1, the next level we have 1 3 3 1 and so on. From here, we see that to get the numbers of the next level, we have to write 1 as the first number, then add 1 to the next number after it in the previous level to get the second number in the next level then add the second number of the previous level to the next number beside it to get the third number in the next level and so on until you get to the last number before 1 in the previous level, add that number to 1 to get the second to the last number in the next level and finally put 1 as the last number in the next level. Now, we have
1 4 6 4 1
1 5 10 10 5 1
And that is the required set of numbers.
It is not.
400 decimeters = 4,000 cm
4,000 cm = 40 m
∠1 and ∠2 are alternate exterior angles where transversal BE crosses parallel lines AC and DF, therefore they are equal. ∠2 and ∠3 are opposite angles of a parallelogram, therefore they are equal.
... ∠1 = ∠2
... 3x -5 = 2x +15 . . . . substitute the given values
... x = 20 . . . . . . . . . . . add 5-2x
The measures of angles 1, 2, and 3 are 2·20+15 = 55 . . . degrees.