Ineed doing this angle homework and i don’t understand a thing.

If you angle at the bottom is 50 that makes the opposite one 50 to and when there is a small square like at the top angle it means it is a 90° angle. 
Since every triangle equals 180° you subtract 140 which is the 2 angles added together and the last angle would be 40°.

The answer is: y would equal 3 because if you simplify the equation then it would be y= 3x+9 and if you divide 3x and 9 by 3 it would equal 3. y= 3