Answer:
![m<D=106\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/br9rpfrpfieqq8r66omh0atp6kbr7zll0c.png)
Explanation:
we know that
In a quadrilateral inscribed in a circle opposite angles are supplementary so
![m<A+m<C=180\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/1waj9ztw1p1bo5fxof457czzrz4l848odp.png)
![m<B+m<D=180\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/mml14uvxmwze9xbvxdq3r597c1y3b1m4zb.png)
Step 1
Find the value of x
substitute the values
![x^(2) +3x=180\\ \\ x^(2) +3x-180=0](https://img.qammunity.org/2020/formulas/mathematics/high-school/xrru74q9ykn7539v05hh295eg0zm4ck180.png)
using a graphing tool
solve the quadratic equation
see the attached figure
![x=12\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/vutqzu7wvassh5dwv21v28r1rwa3hw6pcd.png)
step 2
Find the measure of angle D
![m<B+m<D=180\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/mml14uvxmwze9xbvxdq3r597c1y3b1m4zb.png)
![m<B=7x-10=7(12)-10=74\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/qf0eqbpi0wuq5exey40q7lznvubvxnkhrt.png)
substitute
![74\°+m<D=180\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/xbvgovecj8yri8gb5lystqe27oazdf1agw.png)
![m<D=180\°-74\°=106\°](https://img.qammunity.org/2020/formulas/mathematics/high-school/styiqehbdhlj3b1s01yuht2l02aycr2ms1.png)