Question

Will mark brainliest!!

Answer 1

Solve the system

9x = 27-9y
20x=71-9y

Let's use the "elimination through addition/subtraction method.
Multiply the first equation by -1 so as to obtain +9y:

-9x = -27 + 9y
20x=  71-   9y
--------------------

Add these 2 equations together:

-9x = -27 + 9y
20x=  71-   9y
--------------------
 11x = 44

Solve this for x:  x = 44/11 = 4.

Now find y by subst. 4 for x in either of the original equations.

Using the second equation:     

20x=71-9y
20(4) = 71 - 9y
80-71 = -9y
9 = -9y.  Then y = -1.

The solution set is (4,-1).