Answer:
The length of the third side is 23
Step-by-step explanation:
All check
Note: in the 2nd eqn we are given a formula for x: x = 2y-15. Sub this result into the first eqn; doing so will eliminate x:
-5(2y-15)+4y =3
-10y + 75 + 4y = 3, so -6y = -72. Then y = 12. Solution is (9,12).
Check this by subst.:
Is -5(9)+4(12) = 3?
Is -45 + 48 = 3? YES.
4x + 2x = < y
This is because the opposite sides (which is 4x and 2x) of a triangle add up to the exterior angle (<y).
We have to find X.
As you know:

because the angles of a triangle add up to 180.
When we add them:


The 9 is multiplying with the X. We want X only and not 9 with it. So, when we take 9 to the other side, it becomes divide. As a result, the answer to x is:-

Substitute value of x into 4x and 2x to find the exterior angle:-
4x:

2x:

When we add them we get the answer for angle Y:-

Therefore, we can conclude that:

The couple would get 120,000