If 3x – 9y = 21 and 6x + 3y = 21, which of these could be a value of x or y?

Question

asked Jan 21, 2021 29.2k views

1 Answer

Zdf · Answer 1 · 2021-01-26T10:34:41+0000

Answer: x=4, y=-1

Explanation:

Multiply the second equation by 3:

18x+9y=63

Then summarize both equations 18x+9y+3x-9y=21+63

21x=84 => x=4

use x=4 in any of initial equations ,for instance in first one:

3*4-9*y=21

12-9*y=21

9y=12-21

9y=-9

y=-1