solve for x 19-24. find the measure of the angle indicated in bold for 25-28.

N 19) 
angle (21x+6) is equal angle 90°-----> by alternate exterior angles
so
21x+6=90--------> 21x=84----------> x=4°

the answer  N 19) is 4 degrees

N 20)
angle 75 is equal angle 11x-2-----> by corresponding angles
so
11x-2=75-----> 11x=77--------> x=7°

the answer N 20) is x=7 degrees

N 21)
angle 60 is equal angle (8x-4)------> by alternate interior angles
so
8x-4=60-----> 8x=64--------> x=64/8-----> x=8°

the answer N 21) is x=8 degrees

N 22) 
angle (x+139) is equal to angle 132-----> by alternate interior angles
so
x+139=132-------> x=132-139--------> x=-7 °

the answer N 22) is x=-7 degrees

N 23) 
angle (-1+14x) is equal to angle (12x+17)---->  by alternate exterior angles
so
-1+14x=12x+17------> 14x-12x=17+1----> 2x=18----> x=9

the answer N 23) is x=9 degrees

N 24) 
angle (23x-5) is equal to angle (21x+5)----> by corresponding angles
so
23x-5=21x+5-----> 23x-21x=5+5-----> 2x=10-----> x=5

the answer N 24) is x=5 degrees

N 25)
angle (x+96) and angle (x+96)-------> are supplementary angles
so
x+96+x+96=180--------->2x+192=180------>  x=-6°
the angle indicated in bold is (-6+96)=90°

N 26) 
angle (20x+5) and angle (24x-1)-------> are supplementary angles
so
20x+5+24x-1=180------> 44x=176-----> x=4°
the angle indicated in bold is (20*4+5)=85°

N 27)
angle (6x) is equal to angle (5x+10)--------> by corresponding angles
so
6x=5x+10------> 6x-5x=10------> x=10
the angle indicated in bold is (6*10)=60°

N 28)
angle (x+109) and angle (x+89) are supplementary angles
so
x+109+x+89=180----> 2x=-18-------> x=-9
the angle indicated in bold is (x+89)----> -9+89=80°