I’m rather confused about how to find the value of x. can someone ? ?

The angles within a triangle must equal 180.

180 - (50+91) = 39

Angles on a straight line also must add up to 180.

180 - 39 = 141

So x = 141

First look at the inside of the triangle which always equals 180
141 + x = 180
x = 39
A straight line always equals 180 also
x + 39 = 180
x = 141
The missing value “x” equals 141