Solve for the missing angle below

Answer:
x=21, 5x=105, 3x+12=75
Step-by-step explanation:
5x+(3x+12)=180
8x + 12 =180
8x = 168
x=21
5x=21*5=105
3x+12=3*21+12=63+12=75
Answer:
x = 21
5 x = 105
3 x + 12 = 75
Step-by-step explanation:
Angles on a straight line add to 180° so
5 x + 3 x + 12 = 180
Add the x's together
8 x + 12 = 180
Minus 12 from both sides
8 x = 168
Divide both sides by 8
x = 21
Now we can substitute x into 5 x and 3 x + 12
5 x = 5 × 21 = 105
3 x + 12 = 3 × 21 + 12 = 63 + 12 = 75