Please answer if you know. I need an explanation too and please no links or sites.

we know that

1) the inscribed angle measures half of the arc it comprises.

so

m∠dgf= > expression

2) the opposite angles in an inscribed quadrilateral are supplementary angles

so

m∠dgf=

m∠dgf=°

substitute in the expression to find the value of arc ef

therefore

the answer is

the measure of the arc ef is

seems like it's already there

step-by-step explanation:

x can be -1 and 1 if it's absolute value is just one, so i think you're good.