# Thread: Finding the value of X for two Supplementary Angles

1. ## Finding the value of X for two Supplementary Angles

suppose angles A and B are supplementary angles. Also suppose the measure of angle A is (2x -30)*degrees* and the measure of angle B is (2/3X + 15)*degrees*.

ok what I did was take angle A + B = 180, and solve for the X value. I had to combine the two X values into one ... then isolate X on one side of the equal sign.

my answer was X= 435/8 which in decimal form is 54.375.

2. You can quickly check your answer, by calculating A and B from X, and checking that A + B = 180.

I think you must have made a small mistake since using your value for X, A + B = 130.

3. Originally Posted by sharkfood4
suppose angles A and B are supplementary angles. Also suppose the measure of angle A is (2x -30)*degrees* and the measure of angle B is (2/3X + 15)*degrees*.

ok what I did was take angle A + B = 180, and solve for the X value. I had to combine the two X values into one ... then isolate X on one side of the equal sign.

my answer was X= 435/8 which in decimal form is 54.375.

$A+B=180^o$
$\displaystyle\ 2x-30^o+\frac{2x}{3}+15^o=180^o\Rightarrow\frac{6x}{3 }+\frac{2x}{3}-30^o+15^o=180^o$
$\Rightarrow\displaystyle\frac{8x}{3}-15^o=180^o$
$\displaystyle\Rightarrow\frac{8x}{3}=180^o+15^o$
but somehow you got $180^o-35^o$