12. These are corresponding angles therefore they must be equal for u and v to be parallel
12x-4=10x+10
2x=14
x=7
14. These also must be equal for u and v to be parallel so
19x-4=110
19x=114
x=6
16. Same here, they’re alternate angles so they must be equal
7x+14=8x+6
8=x
18. If x=25 then both angles would be greater than 180 degrees so x cannot equal 25.
