Question

I need help! (It's easy)

Answer 1

A.) it's a 90° angle 
     90=6x+4x+10
     90=10x+10
    -10         -10
     80=10x
     divide both sides by 10, x=8
B.) it's a 180° angle
     180=5x+13+3x+7
     180=8x+20
     -20        -20
     160=8x
     divide both sides by 8, x=20
C.) it's a 180° angle
     180=3x+5+2x+18+2x+17
     180=7x+40
     -40        -40
     140=7x
     divide both sides by 7, x=20
D.) it's a 180° angle
     180=90+30+x
     180=120+x
     -120  -120
     60=x