The sum of all the angles of a triangle is 180 degrees. To solve for y you can make a formula of the sum of the angles equal to 180 like so...
y + 10 + 2y + 50 = 180
Now you must combine like terms. This means that first numbers with the same variables (y) must be combined...
(y + 2y) + 10 + 50 = 180
3y + 10 + 50 = 180
Combine like terms 10 and 50...
3y + 60 = 180
Now bring 60 to the left side by subtracting 60 to both sides (what you do on one side you must do to the other). Since 60 is being added on the left side, subtraction (the opposite of addition) will cancel it out (make it zero) from the left side and bring it over to the right side.
3y + 60 - 60 = 180 - 60
3y + 0 = 120
3y = 120
Next divide 3 to both sides to finish isolating x. Since 3 is being multiplied by x, division (the opposite of multiplication) will cancel 3 out (in this case it will make 3 one) from the left side and bring it over to the right side.
3y / 3 = 120 / 3
y = 40
C. 40
Hope this helped!
~Just a girl in love with Shawn Mendes
