quadrilateral abcd is inscribed in this circle.
what is the measure of angle a?

enter your answer in the box.

°

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"

It's like discovering the answer to a puzzle. the purpose in solving an equation is to find the value or values of the variable that makes it a true statement. any value of the variable that makes the equation true is called a solution to the equation.