You haven't provided the graph, therefore, I cannot give an exact answer. However, I will help you with the concept.
A solution to a system of equations would be one or more order pairs that satisfy <u><em>ALL</em></u> equations given in the system.
<u>There are two ways to get the solution of a system of equations:</u> <u>1- algebraically: </u> This would be by solving the equations in the system simultaneously using elimination/substitution,...etc
<u>2- graphically:</u> This would be by graphing all the equations given in the system and finding the points of intersection between the graphs. <u>Note that:</u> If the given system has two equations, then we need to find the point(s) of intersection between the two graphs If the given system has three equations, then we need to find the point(s) of intersection between the three graphs
Therefore, for your question, all you have to do is find the point(s) of intersection between your graphs.
First lets solve for x we know 3x=90. In this case x=30. Now we can solve for y. We know the triangle needs to equal 180 so y+2(30)=180. So we get y=120. Hope it helps