Answer:
D) 55°.
Step-by-step explanation:
The sum of angles in a triangle add up to 180°.
[tex]y+(y+30)+40=180[/tex]
[tex]2y+70=180\\[/tex]
Subtract 70 from both sides:
[tex]2y+70-70=180-70[/tex]
[tex]2y=110[/tex]
Divide both sides by 2:
[tex]\frac{2y}{2}=\frac{110}{2}[/tex]
[tex]y=55[/tex]
