Question

problem 18: (first taught in lesson 24)
find x and y.
after you enter your answer press go.
x =
y =

Explanation:

Step1: Use the property of angles in a straight - line

The angles on a straight - line sum to 180°. So, $3y+100 = 180$.
$3y=180 - 100$
$3y = 80$
$y=\frac{80}{3}$

Step2: Use the angle - sum property of a triangle

The sum of interior angles of a triangle is 180°. For the left - hand triangle, $2x + 4x+3y=180$. Substitute $y = \frac{80}{3}$ into the equation.
$2x+4x + 3\times\frac{80}{3}=180$
$6x+80 = 180$
$6x=180 - 80$
$6x = 100$
$x = 20$

Answer:

$x = 20$, $y = \frac{80}{3}$