Answer:
[tex]90^{\circ}[/tex]
Step-by-step explanation:
The interior angles of all triangles sum up to [tex]180^{\circ}[/tex]. Therefore, we can write the following equation:
[tex]4x+5x+9x=180[/tex], where [tex]x[/tex] is some constant.
Combining like terms, we have [tex]18x=180,\: x=10[/tex].
Therefore, the angles of this triangle are [tex]4(10)=40^{\circ}, \: 5(10)=50^{\circ}, \: 9(10)=90^{\circ}[/tex], the largest of them being [tex]\fbox{$90^{\circ}$}[/tex].
