applications of systems of linear equestions (word problems)

[leannasales]

can anyone help me to set up my problem? it is a drawing of a right triangle with the angles x, y, and 90 degrees. angle y is supplementary to 3x+10 degrees. i know that angles x,y, and 90 =180 and angles y and 3x+10 =180 also. my two formulas i wrote are x+y+90=180 and y+3x+10=180. i dont understand the next step to do. the book says the answers are x=40 and y=50. can snyone help me with the next step? here is a picture number 7.

 

[stapel]

my two formulas i wrote are x+y+90=180 and y+3x+10=180. i dont understand the next step to do.

Now solve the system of linear equations.

 

[leannasales]

thank you for the help

 

[srmichael]

Another way to do this is to recognize that the exterior angle af any angle in a triangle is equal to the sum of the two interior angles, where neither of the two interior angles are adjacent to the exterior angle.

Thus:

3x + 10 = 90 + x

2x = 80

x = 40