You have the next triangle:
As the triangle has two angles that are congruent, then it is a isisceles triangle. The opposite sides of the equal angles have the same measure.
Sides FG and GH have the same measure:
![FG\cong GH](https://img.qammunity.org/2023/formulas/mathematics/college/4rpxdly5m3f4c1ugxgfaxvbjvn93wkwaxe.png)
![x+40=2x+20](https://img.qammunity.org/2023/formulas/mathematics/college/qko81bk00ia5xoaq0pj7x7ny75pg36m4pe.png)
Use this equation to find the value of x:
- Substract in both sides of the equation 2x:
![\begin{gathered} x-2x+40=2x-2x+20 \\ -x+40=20 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/8lsxn2ba3pesfz63ztaghb27lu39v87r09.png)
- Substract in both sides of the equation 40:
![\begin{gathered} -x+40-40=20-40 \\ -x=-20 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/dm3oqgm3kmgb43drbaxf6e8bterz6507z4.png)
- Multiply both sides of the equation by -1:
![\begin{gathered} (-1)(-x)=(-1)(-20) \\ \\ x=20 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/1tkrtmfi4lnk6o3lgdvp1mv25j7b6652xg.png)
Answer x=20