3x + 4y = –20
6x + 5y = –7

x = 8

y = -11

Step-by-step explanation:

In this question, we have to find out the value of "x" and "y".

Solve:

Lets solve for y first.

-2(3x + 4y = -20)

6x + 5y = -7

-6x - 8y = 40

6x + 5y = -7

-3y = 33

Divide both sides by -3

y = -11

We now know what the value of "y" is, now we must find the value of x. To do this, we would plug -11 to "y" in one of our equations.

Solve for x:

3x + 4y = -20

3x + 4(-11) = -20

3x - 44 = -20

Add 44 to both sides.

3x = 24

Divide both sides by 3

x = 8

Now we know that our answer are:

x = 8

y = -11

As above angles are supplementary,

Hence, value of x is 60°.