A quadrilateral, has 4 sides and its internal angles sum, add up to 360, now... you have 3 angles give.. .but we don't have C
so.. C is the difference of all the three angles from 360 or
whatever that is, now, you'll get some value in x-terms
so.... now once we know what C is
you can if you want, do a search in google for "inscribed quadrilateral conjecture", I can do a quick proof if you need one
but in short, for a quadrilateral inscribed in a circle, each pair of opposites angles are "supplementary angles", namely they add up to 180°
so.. what the dickens does all that mean? well D+B=180 and A+C = 180
now. we know what A is, 2x+1
and by now, you'd know what C is from 360-x-2x-1-148
so... add them together then and
solve for "x"
so.. C is the difference of all the three angles from 360 or
so.... now once we know what C is
you can if you want, do a search in google for "inscribed quadrilateral conjecture", I can do a quick proof if you need one
but in short, for a quadrilateral inscribed in a circle, each pair of opposites angles are "supplementary angles", namely they add up to 180°
so.. what the dickens does all that mean? well D+B=180 and A+C = 180
now. we know what A is, 2x+1
and by now, you'd know what C is from 360-x-2x-1-148
so... add them together then and
solve for "x"